/*
* Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util;
import java.io.Serializable;
import java.io.ObjectOutputStream;
import java.io.IOException;
import java.lang.reflect.Array;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.UnaryOperator;
import java.util.stream.IntStream;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
* This class consists exclusively of static methods that operate on or return
* collections. It contains polymorphic algorithms that operate on
* collections, "wrappers", which return a new collection backed by a
* specified collection, and a few other odds and ends.
*
* <p>The methods of this class all throw a <tt>NullPointerException</tt>
* if the collections or class objects provided to them are null.
*
* <p>The documentation for the polymorphic algorithms contained in this class
* generally includes a brief description of the <i>implementation</i>. Such
* descriptions should be regarded as <i>implementation notes</i>, rather than
* parts of the <i>specification</i>. Implementors should feel free to
* substitute other algorithms, so long as the specification itself is adhered
* to. (For example, the algorithm used by <tt>sort</tt> does not have to be
* a mergesort, but it does have to be <i>stable</i>.)
*
* <p>The "destructive" algorithms contained in this class, that is, the
* algorithms that modify the collection on which they operate, are specified
* to throw <tt>UnsupportedOperationException</tt> if the collection does not
* support the appropriate mutation primitive(s), such as the <tt>set</tt>
* method. These algorithms may, but are not required to, throw this
* exception if an invocation would have no effect on the collection. For
* example, invoking the <tt>sort</tt> method on an unmodifiable list that is
* already sorted may or may not throw <tt>UnsupportedOperationException</tt>.
*
* <p>This class is a member of the
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
* Java Collections Framework</a>.
*
* @author Josh Bloch
* @author Neal Gafter
* @see Collection
* @see Set
* @see List
* @see Map
* @since 1.2
*/
public class Collections {
// Suppresses default constructor, ensuring non-instantiability.
private Collections() {
}
// Algorithms
/*
* Tuning parameters for algorithms - Many of the List algorithms have
* two implementations, one of which is appropriate for RandomAccess
* lists, the other for "sequential." Often, the random access variant
* yields better performance on small sequential access lists. The
* tuning parameters below determine the cutoff point for what constitutes
* a "small" sequential access list for each algorithm. The values below
* were empirically determined to work well for LinkedList. Hopefully
* they should be reasonable for other sequential access List
* implementations. Those doing performance work on this code would
* do well to validate the values of these parameters from time to time.
* (The first word of each tuning parameter name is the algorithm to which
* it applies.)
*/
private static final int BINARYSEARCH_THRESHOLD = 5000;
private static final int REVERSE_THRESHOLD = 18;
private static final int SHUFFLE_THRESHOLD = 5;
private static final int FILL_THRESHOLD = 25;
private static final int ROTATE_THRESHOLD = 100;
private static final int COPY_THRESHOLD = 10;
private static final int REPLACEALL_THRESHOLD = 11;
private static final int INDEXOFSUBLIST_THRESHOLD = 35;
/**
* Sorts the specified list into ascending order, according to the
* {@linkplain Comparable natural ordering} of its elements.
* All elements in the list must implement the {@link Comparable}
* interface. Furthermore, all elements in the list must be
* <i>mutually comparable</i> (that is, {@code e1.compareTo(e2)}
* must not throw a {@code ClassCastException} for any elements
* {@code e1} and {@code e2} in the list).
*
* <p>This sort is guaranteed to be <i>stable</i>: equal elements will
* not be reordered as a result of the sort.
*
* <p>The specified list must be modifiable, but need not be resizable.
*
* @implNote
* This implementation defers to the {@link List#sort(Comparator)}
* method using the specified list and a {@code null} comparator.
*
* @param <T> the class of the objects in the list
* @param list the list to be sorted.
* @throws ClassCastException if the list contains elements that are not
* <i>mutually comparable</i> (for example, strings and integers).
* @throws UnsupportedOperationException if the specified list's
* list-iterator does not support the {@code set} operation.
* @throws IllegalArgumentException (optional) if the implementation
* detects that the natural ordering of the list elements is
* found to violate the {@link Comparable} contract
* @see List#sort(Comparator)
*/
@SuppressWarnings("unchecked")
public static <T extends Comparable<? super T>> void sort(List<T> list) {
list.sort(null);
}
/**
* Sorts the specified list according to the order induced by the
* specified comparator. All elements in the list must be <i>mutually
* comparable</i> using the specified comparator (that is,
* {@code c.compare(e1, e2)} must not throw a {@code ClassCastException}
* for any elements {@code e1} and {@code e2} in the list).
*
* <p>This sort is guaranteed to be <i>stable</i>: equal elements will
* not be reordered as a result of the sort.
*
* <p>The specified list must be modifiable, but need not be resizable.
*
* @implNote
* This implementation defers to the {@link List#sort(Comparator)}
* method using the specified list and comparator.
*
* @param <T> the class of the objects in the list
* @param list the list to be sorted.
* @param c the comparator to determine the order of the list. A
* {@code null} value indicates that the elements' <i>natural
* ordering</i> should be used.
* @throws ClassCastException if the list contains elements that are not
* <i>mutually comparable</i> using the specified comparator.
* @throws UnsupportedOperationException if the specified list's
* list-iterator does not support the {@code set} operation.
* @throws IllegalArgumentException (optional) if the comparator is
* found to violate the {@link Comparator} contract
* @see List#sort(Comparator)
*/
@SuppressWarnings({"unchecked", "rawtypes"})
public static <T> void sort(List<T> list, Comparator<? super T> c) {
list.sort(c);
}
/**
* Searches the specified list for the specified object using the binary
* search algorithm. The list must be sorted into ascending order
* according to the {@linkplain Comparable natural ordering} of its
* elements (as by the {@link #sort(List)} method) prior to making this
* call. If it is not sorted, the results are undefined. If the list
* contains multiple elements equal to the specified object, there is no
* guarantee which one will be found.
*
* <p>This method runs in log(n) time for a "random access" list (which
* provides near-constant-time positional access). If the specified list
* does not implement the {@link RandomAccess} interface and is large,
* this method will do an iterator-based binary search that performs
* O(n) link traversals and O(log n) element comparisons.
*
* @param <T> the class of the objects in the list
* @param list the list to be searched.
* @param key the key to be searched for.
* @return the index of the search key, if it is contained in the list;
* otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The
* <i>insertion point</i> is defined as the point at which the
* key would be inserted into the list: the index of the first
* element greater than the key, or <tt>list.size()</tt> if all
* elements in the list are less than the specified key. Note
* that this guarantees that the return value will be >= 0 if
* and only if the key is found.
* @throws ClassCastException if the list contains elements that are not
* <i>mutually comparable</i> (for example, strings and
* integers), or the search key is not mutually comparable
* with the elements of the list.
*/
public static <T>
int binarySearch(List<? extends Comparable<? super T>> list, T key) {
if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
return Collections.indexedBinarySearch(list, key);
else
return Collections.iteratorBinarySearch(list, key);
}
private static <T>
int indexedBinarySearch(List<? extends Comparable<? super T>> list, T key) {
int low = 0;
int high = list.size()-1;
while (low <= high) {
int mid = (low + high) >>> 1;
Comparable<? super T> midVal = list.get(mid);
int cmp = midVal.compareTo(key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
private static <T>
int iteratorBinarySearch(List<? extends Comparable<? super T>> list, T key)
{
int low = 0;
int high = list.size()-1;
ListIterator<? extends Comparable<? super T>> i = list.listIterator();
while (low <= high) {
int mid = (low + high) >>> 1;
Comparable<? super T> midVal = get(i, mid);
int cmp = midVal.compareTo(key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
/**
* Gets the ith element from the given list by repositioning the specified
* list listIterator.
*/
private static <T> T get(ListIterator<? extends T> i, int index) {
T obj = null;
int pos = i.nextIndex();
if (pos <= index) {
do {
obj = i.next();
} while (pos++ < index);
} else {
do {
obj = i.previous();
} while (--pos > index);
}
return obj;
}
/**
* Searches the specified list for the specified object using the binary
* search algorithm. The list must be sorted into ascending order
* according to the specified comparator (as by the
* {@link #sort(List, Comparator) sort(List, Comparator)}
* method), prior to making this call. If it is
* not sorted, the results are undefined. If the list contains multiple
* elements equal to the specified object, there is no guarantee which one
* will be found.
*
* <p>This method runs in log(n) time for a "random access" list (which
* provides near-constant-time positional access). If the specified list
* does not implement the {@link RandomAccess} interface and is large,
* this method will do an iterator-based binary search that performs
* O(n) link traversals and O(log n) element comparisons.
*
* @param <T> the class of the objects in the list
* @param list the list to be searched.
* @param key the key to be searched for.
* @param c the comparator by which the list is ordered.
* A <tt>null</tt> value indicates that the elements'
* {@linkplain Comparable natural ordering} should be used.
* @return the index of the search key, if it is contained in the list;
* otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The
* <i>insertion point</i> is defined as the point at which the
* key would be inserted into the list: the index of the first
* element greater than the key, or <tt>list.size()</tt> if all
* elements in the list are less than the specified key. Note
* that this guarantees that the return value will be >= 0 if
* and only if the key is found.
* @throws ClassCastException if the list contains elements that are not
* <i>mutually comparable</i> using the specified comparator,
* or the search key is not mutually comparable with the
* elements of the list using this comparator.
*/
@SuppressWarnings("unchecked")
public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c) {
if (c==null)
return binarySearch((List<? extends Comparable<? super T>>) list, key);
if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
return Collections.indexedBinarySearch(list, key, c);
else
return Collections.iteratorBinarySearch(list, key, c);
}
private static <T> int indexedBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
int low = 0;
int high = l.size()-1;
while (low <= high) {
int mid = (low + high) >>> 1;
T midVal = l.get(mid);
int cmp = c.compare(midVal, key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
private static <T> int iteratorBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
int low = 0;
int high = l.size()-1;
ListIterator<? extends T> i = l.listIterator();
while (low <= high) {
int mid = (low + high) >>> 1;
T midVal = get(i, mid);
int cmp = c.compare(midVal, key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
/**
* Reverses the order of the elements in the specified list.<p>
*
* This method runs in linear time.
*
* @param list the list whose elements are to be reversed.
* @throws UnsupportedOperationException if the specified list or
* its list-iterator does not support the <tt>set</tt> operation.
*/
@SuppressWarnings({"rawtypes", "unchecked"})
public static void reverse(List<?> list) {
int size = list.size();
if (size < REVERSE_THRESHOLD || list instanceof RandomAccess) {
for (int i=0, mid=size>>1, j=size-1; i<mid; i++, j--)
swap(list, i, j);
} else {
// instead of using a raw type here, it's possible to capture
// the wildcard but it will require a call to a supplementary
// private method
ListIterator fwd = list.listIterator();
ListIterator rev = list.listIterator(size);
for (int i=0, mid=list.size()>>1; i<mid; i++) {
Object tmp = fwd.next();
fwd.set(rev.previous());
rev.set(tmp);
}
}
}
/**
* Randomly permutes the specified list using a default source of
* randomness. All permutations occur with approximately equal
* likelihood.
*
* <p>The hedge "approximately" is used in the foregoing description because
* default source of randomness is only approximately an unbiased source
* of independently chosen bits. If it were a perfect source of randomly
* chosen bits, then the algorithm would choose permutations with perfect
* uniformity.
*
* <p>This implementation traverses the list backwards, from the last
* element up to the second, repeatedly swapping a randomly selected element
* into the "current position". Elements are randomly selected from the
* portion of the list that runs from the first element to the current
* position, inclusive.
*
* <p>This method runs in linear time. If the specified list does not
* implement the {@link RandomAccess} interface and is large, this
* implementation dumps the specified list into an array before shuffling
* it, and dumps the shuffled array back into the list. This avoids the
* quadratic behavior that would result from shuffling a "sequential
* access" list in place.
*
* @param list the list to be shuffled.
* @throws UnsupportedOperationException if the specified list or
* its list-iterator does not support the <tt>set</tt> operation.
*/
public static void shuffle(List<?> list) {
Random rnd = r;
if (rnd == null)
r = rnd = new Random(); // harmless race.
shuffle(list, rnd);
}
private static Random r;
/**
* Randomly permute the specified list using the specified source of
* randomness. All permutations occur with equal likelihood
* assuming that the source of randomness is fair.<p>
*
* This implementation traverses the list backwards, from the last element
* up to the second, repeatedly swapping a randomly selected element into
* the "current position". Elements are randomly selected from the
* portion of the list that runs from the first element to the current
* position, inclusive.<p>
*
* This method runs in linear time. If the specified list does not
* implement the {@link RandomAccess} interface and is large, this
* implementation dumps the specified list into an array before shuffling
* it, and dumps the shuffled array back into the list. This avoids the
* quadratic behavior that would result from shuffling a "sequential
* access" list in place.
*
* @param list the list to be shuffled.
* @param rnd the source of randomness to use to shuffle the list.
* @throws UnsupportedOperationException if the specified list or its
* list-iterator does not support the <tt>set</tt> operation.
*/
@SuppressWarnings({"rawtypes", "unchecked"})
public static void shuffle(List<?> list, Random rnd) {
int size = list.size();
if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) {
for (int i=size; i>1; i--)
swap(list, i-1, rnd.nextInt(i));
} else {
Object arr[] = list.toArray();
// Shuffle array
for (int i=size; i>1; i--)
swap(arr, i-1, rnd.nextInt(i));
// Dump array back into list
// instead of using a raw type here, it's possible to capture
// the wildcard but it will require a call to a supplementary
// private method
ListIterator it = list.listIterator();
for (int i=0; i<arr.length; i++) {
it.next();
it.set(arr[i]);
}
}
}
/**
* Swaps the elements at the specified positions in the specified list.
* (If the specified positions are equal, invoking this method leaves
* the list unchanged.)
*
* @param list The list in which to swap elements.
* @param i the index of one element to be swapped.
* @param j the index of the other element to be swapped.
* @throws IndexOutOfBoundsException if either <tt>i</tt> or <tt>j</tt>
* is out of range (i < 0 || i >= list.size()
* || j < 0 || j >= list.size()).
* @since 1.4
*/
@SuppressWarnings({"rawtypes", "unchecked"})
public static void swap(List<?> list, int i, int j) {
// instead of using a raw type here, it's possible to capture
// the wildcard but it will require a call to a supplementary
// private method
final List l = list;
l.set(i, l.set(j, l.get(i)));
}
/**
* Swaps the two specified elements in the specified array.
*/
private static void swap(Object[] arr, int i, int j) {
Object tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
/**
* Replaces all of the elements of the specified list with the specified
* element. <p>
*
* This method runs in linear time.
*
* @param <T> the class of the objects in the list
* @param list the list to be filled with the specified element.
* @param obj The element with which to fill the specified list.
* @throws UnsupportedOperationException if the specified list or its
* list-iterator does not support the <tt>set</tt> operation.
*/
public static <T> void fill(List<? super T> list, T obj) {
int size = list.size();
if (size < FILL_THRESHOLD || list instanceof RandomAccess) {
for (int i=0; i<size; i++)
list.set(i, obj);
} else {
ListIterator<? super T> itr = list.listIterator();
for (int i=0; i<size; i++) {
itr.next();
itr.set(obj);
}
}
}
/**
* Copies all of the elements from one list into another. After the
* operation, the index of each copied element in the destination list
* will be identical to its index in the source list. The destination
* list must be at least as long as the source list. If it is longer, the
* remaining elements in the destination list are unaffected. <p>
*
* This method runs in linear time.
*
* @param <T> the class of the objects in the lists
* @param dest The destination list.
* @param src The source list.
* @throws IndexOutOfBoundsException if the destination list is too small
* to contain the entire source List.
* @throws UnsupportedOperationException if the destination list's
* list-iterator does not support the <tt>set</tt> operation.
*/
public static <T> void copy(List<? super T> dest, List<? extends T> src) {
int srcSize = src.size();
if (srcSize > dest.size())
throw new IndexOutOfBoundsException("Source does not fit in dest");
if (srcSize < COPY_THRESHOLD ||
(src instanceof RandomAccess && dest instanceof RandomAccess)) {
for (int i=0; i<srcSize; i++)
dest.set(i, src.get(i));
} else {
ListIterator<? super T> di=dest.listIterator();
ListIterator<? extends T> si=src.listIterator();
for (int i=0; i<srcSize; i++) {
di.next();
di.set(si.next());
}
}
}
/**
* Returns the minimum element of the given collection, according to the
* <i>natural ordering</i> of its elements. All elements in the
* collection must implement the <tt>Comparable</tt> interface.
* Furthermore, all elements in the collection must be <i>mutually
* comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
* <tt>e2</tt> in the collection).<p>
*
* This method iterates over the entire collection, hence it requires
* time proportional to the size of the collection.
*
* @param <T> the class of the objects in the collection
* @param coll the collection whose minimum element is to be determined.
* @return the minimum element of the given collection, according
* to the <i>natural ordering</i> of its elements.
* @throws ClassCastException if the collection contains elements that are
* not <i>mutually comparable</i> (for example, strings and
* integers).
* @throws NoSuchElementException if the collection is empty.
* @see Comparable
*/
public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll) {
Iterator<? extends T> i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (next.compareTo(candidate) < 0)
candidate = next;
}
return candidate;
}
/**
* Returns the minimum element of the given collection, according to the
* order induced by the specified comparator. All elements in the
* collection must be <i>mutually comparable</i> by the specified
* comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
* <tt>e2</tt> in the collection).<p>
*
* This method iterates over the entire collection, hence it requires
* time proportional to the size of the collection.
*
* @param <T> the class of the objects in the collection
* @param coll the collection whose minimum element is to be determined.
* @param comp the comparator with which to determine the minimum element.
* A <tt>null</tt> value indicates that the elements' <i>natural
* ordering</i> should be used.
* @return the minimum element of the given collection, according
* to the specified comparator.
* @throws ClassCastException if the collection contains elements that are
* not <i>mutually comparable</i> using the specified comparator.
* @throws NoSuchElementException if the collection is empty.
* @see Comparable
*/
@SuppressWarnings({"unchecked", "rawtypes"})
public static <T> T min(Collection<? extends T> coll, Comparator<? super T> comp) {
if (comp==null)
return (T)min((Collection) coll);
Iterator<? extends T> i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (comp.compare(next, candidate) < 0)
candidate = next;
}
return candidate;
}
/**
* Returns the maximum element of the given collection, according to the
* <i>natural ordering</i> of its elements. All elements in the
* collection must implement the <tt>Comparable</tt> interface.
* Furthermore, all elements in the collection must be <i>mutually
* comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
* <tt>e2</tt> in the collection).<p>
*
* This method iterates over the entire collection, hence it requires
* time proportional to the size of the collection.
*
* @param <T> the class of the objects in the collection
* @param coll the collection whose maximum element is to be determined.
* @return the maximum element of the given collection, according
* to the <i>natural ordering</i> of its elements.
* @throws ClassCastException if the collection contains elements that are
* not <i>mutually comparable</i> (for example, strings and
* integers).
* @throws NoSuchElementException if the collection is empty.
* @see Comparable
*/
public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) {
Iterator<? extends T> i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (next.compareTo(candidate) > 0)
candidate = next;
}
return candidate;
}
/**
* Returns the maximum element of the given collection, according to the
* order induced by the specified comparator. All elements in the
* collection must be <i>mutually comparable</i> by the specified
* comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
* <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
* <tt>e2</tt> in the collection).<p>
*
* This method iterates over the entire collection, hence it requires
* time proportional to the size of the collection.
*
* @param <T> the class of the objects in the collection
* @param coll the collection whose maximum element is to be determined.
* @param comp the comparator with which to determine the maximum element.
* A <tt>null</tt> value indicates that the elements' <i>natural
* ordering</i> should be used.
* @return the maximum element of the given collection, according
* to the specified comparator.
* @throws ClassCastException if the collection contains elements that are
* not <i>mutually comparable</i> using the specified comparator.
* @throws NoSuchElementException if the collection is empty.
* @see Comparable
*/
@SuppressWarnings({"unchecked", "rawtypes"})
public static <T> T max(Collection<? extends T> coll, Comparator<? super T> comp) {
if (comp==null)
return (T)max((Collection) coll);
Iterator<? extends T> i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (comp.compare(next, candidate) > 0)
candidate = next;
}
return candidate;
}
/**
* Rotates the elements in the specified list by the specified distance.
* After calling this method, the element at index <tt>i</tt> will be
* the element previously at index <tt>(i - distance)</tt> mod
* <tt>list.size()</tt>, for all values of <tt>i</tt> between <tt>0</tt>
* and <tt>list.size()-1</tt>, inclusive. (This method has no effect on
* the size of the list.)
*
* <p>For example, suppose <tt>list</tt> comprises<tt> [t, a, n, k, s]</tt>.
* After invoking <tt>Collections.rotate(list, 1)</tt> (or
* <tt>Collections.rotate(list, -4)</tt>), <tt>list</tt> will comprise
* <tt>[s, t, a, n, k]</tt>.
*
* <p>Note that this method can usefully be applied to sublists to
* move one or more elements within a list while preserving the
* order of the remaining elements. For example, the following idiom
* moves the element at index <tt>j</tt> forward to position
* <tt>k</tt> (which must be greater than or equal to <tt>j</tt>):
* <pre>
* Collections.rotate(list.subList(j, k+1), -1);
* </pre>
* To make this concrete, suppose <tt>list</tt> comprises
* <tt>[a, b, c, d, e]</tt>. To move the element at index <tt>1</tt>
* (<tt>b</tt>) forward two positions, perform the following invocation:
* <pre>
* Collections.rotate(l.subList(1, 4), -1);
* </pre>
* The resulting list is <tt>[a, c, d, b, e]</tt>.
*
* <p>To move more than one element forward, increase the absolute value
* of the rotation distance. To move elements backward, use a positive
* shift distance.
*
* <p>If the specified list is small or implements the {@link
* RandomAccess} interface, this implementation exchanges the first
* element into the location it should go, and then repeatedly exchanges
* the displaced element into the location it should go until a displaced
* element is swapped into the first element. If necessary, the process
* is repeated on the second and successive elements, until the rotation
* is complete. If the specified list is large and doesn't implement the
* <tt>RandomAccess</tt> interface, this implementation breaks the
* list into two sublist views around index <tt>-distance mod size</tt>.
* Then the {@link #reverse(List)} method is invoked on each sublist view,
* and finally it is invoked on the entire list. For a more complete
* description of both algorithms, see Section 2.3 of Jon Bentley's
* <i>Programming Pearls</i> (Addison-Wesley, 1986).
*
* @param list the list to be rotated.
* @param distance the distance to rotate the list. There are no
* constraints on this value; it may be zero, negative, or
* greater than <tt>list.size()</tt>.
* @throws UnsupportedOperationException if the specified list or
* its list-iterator does not support the <tt>set</tt> operation.
* @since 1.4
*/
public static void rotate(List<?> list, int distance) {
if (list instanceof RandomAccess || list.size() < ROTATE_THRESHOLD)
rotate1(list, distance);
else
rotate2(list, distance);
}
private static <T> void rotate1(List<T> list, int distance) {
int size = list.size();
if (size == 0)
return;
distance = distance % size;
if (distance < 0)
distance += size;
if (distance == 0)
return;
for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) {
T displaced = list.get(cycleStart);
int i = cycleStart;
do {
i += distance;
if (i >= size)
i -= size;
displaced = list.set(i, displaced);
nMoved ++;
} while (i != cycleStart);
}
}
private static void rotate2(List<?> list, int distance) {
int size = list.size();
if (size == 0)
return;
int mid = -distance % size;
if (mid < 0)
mid += size;
if (mid == 0)
return;
reverse(list.subList(0, mid));
reverse(list.subList(mid, size));
reverse(list);
}
/**
* Replaces all occurrences of one specified value in a list with another.
* More formally, replaces with <tt>newVal</tt> each element <tt>e</tt>
* in <tt>list</tt> such that
* <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>.
* (This method has no effect on the size of the list.)
*
* @param <T> the class of the objects in the list
* @param list the list in which replacement is to occur.
* @param oldVal the old value to be replaced.
* @param newVal the new value with which <tt>oldVal</tt> is to be
* replaced.
* @return <tt>true</tt> if <tt>list</tt> contained one or more elements
* <tt>e</tt> such that
* <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>.
* @throws UnsupportedOperationException if the specified list or
* its list-iterator does not support the <tt>set</tt> operation.
* @since 1.4
*/
public static <T> boolean replaceAll(List<T> list, T oldVal, T newVal) {
boolean result = false;
int size = list.size();
if (size < REPLACEALL_THRESHOLD || list instanceof RandomAccess) {
if (oldVal==null) {
for (int i=0; i<size; i++) {
if (list.get(i)==null) {
list.set(i, newVal);
result = true;
}
}
} else {
for (int i=0; i<size; i++) {
if (oldVal.equals(list.get(i))) {
list.set(i, newVal);
result = true;
}
}
}
} else {
ListIterator<T> itr=list.listIterator();
if (oldVal==null) {
for (int i=0; i<size; i++) {
if (itr.next()==null) {
itr.set(newVal);
result = true;
}
}
} else {
for (int i=0; i<size; i++) {
if (oldVal.equals(itr.next())) {
itr.set(newVal);
result = true;
}
}
}
}
return result;
}
/**
* Returns the starting position of the first occurrence of the specified
* target list within the specified source list, or -1 if there is no
* such occurrence. More formally, returns the lowest index <tt>i</tt>
* such that {@code source.subList(i, i+target.size()).equals(target)},
* or -1 if there is no such index. (Returns -1 if
* {@code target.size() > source.size()})
*
* <p>This implementation uses the "brute force" technique of scanning
* over the source list, looking for a match with the target at each
* location in turn.
*
* @param source the list in which to search for the first occurrence
* of <tt>target</tt>.
* @param target the list to search for as a subList of <tt>source</tt>.
* @return the starting position of the first occurrence of the specified
* target list within the specified source list, or -1 if there
* is no such occurrence.
* @since 1.4
*/
public static int indexOfSubList(List<?> source, List<?> target) {
int sourceSize = source.size();
int targetSize = target.size();
int maxCandidate = sourceSize - targetSize;
if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
(source instanceof RandomAccess&&target instanceof RandomAccess)) {
nextCand:
for (int candidate = 0; candidate <= maxCandidate; candidate++) {
for (int i=0, j=candidate; i<targetSize; i++, j++)
if (!eq(target.get(i), source.get(j)))
continue nextCand; // Element mismatch, try next cand
return candidate; // All elements of candidate matched target
}
} else { // Iterator version of above algorithm
ListIterator<?> si = source.listIterator();
nextCand:
for (int candidate = 0; candidate <= maxCandidate; candidate++) {
ListIterator<?> ti = target.listIterator();
for (int i=0; i<targetSize; i++) {
if (!eq(ti.next(), si.next())) {
// Back up source iterator to next candidate
for (int j=0; j<i; j++)
si.previous();
continue nextCand;
}
}
return candidate;
}
}
return -1; // No candidate matched the target
}
/**
* Returns the starting position of the last occurrence of the specified
* target list within the specified source list, or -1 if there is no such
* occurrence. More formally, returns the highest index <tt>i</tt>
* such that {@code source.subList(i, i+target.size()).equals(target)},
* or -1 if there is no such index. (Returns -1 if
* {@code target.size() > source.size()})
*
* <p>This implementation uses the "brute force" technique of iterating
* over the source list, looking for a match with the target at each
* location in turn.
*
* @param source the list in which to search for the last occurrence
* of <tt>target</tt>.
* @param target the list to search for as a subList of <tt>source</tt>.
* @return the starting position of the last occurrence of the specified
* target list within the specified source list, or -1 if there
* is no such occurrence.
* @since 1.4
*/
public static int lastIndexOfSubList(List<?> source, List<?> target) {
int sourceSize = source.size();
int targetSize = target.size();
int maxCandidate = sourceSize - targetSize;
if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
source instanceof RandomAccess) { // Index access version
nextCand:
for (int candidate = maxCandidate; candidate >= 0; candidate--) {
for (int i=0, j=candidate; i<targetSize; i++, j++)
if (!eq(target.get(i), source.get(j)))
continue nextCand; // Element mismatch, try next cand
return candidate; // All elements of candidate matched target
}
} else { // Iterator version of above algorithm
if (maxCandidate < 0)
return -1;
ListIterator<?> si = source.listIterator(maxCandidate);
nextCand:
for (int candidate = maxCandidate; candidate >= 0; candidate--) {
ListIterator<?> ti = target.listIterator();
for (int i=0; i<targetSize; i++) {
if (!eq(ti.next(), si.next())) {
if (candidate != 0) {
// Back up source iterator to next candidate
for (int j=0; j<=i+1; j++)
si.previous();
}
continue nextCand;
}
}
return candidate;
}
}
return -1; // No candidate matched the target
}
// Unmodifiable Wrappers
/**
* Returns an unmodifiable view of the specified collection. This method
* allows modules to provide users with "read-only" access to internal
* collections. Query operations on the returned collection "read through"
* to the specified collection, and attempts to modify the returned
* collection, whether direct or via its iterator, result in an
* <tt>UnsupportedOperationException</tt>.<p>
*
* The returned collection does <i>not</i> pass the hashCode and equals
* operations through to the backing collection, but relies on
* <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods. This
* is necessary to preserve the contracts of these operations in the case
* that the backing collection is a set or a list.<p>
*
* The returned collection will be serializable if the specified collection
* is serializable.
*
* @param <T> the class of the objects in the collection
* @param c the collection for which an unmodifiable view is to be
* returned.
* @return an unmodifiable view of the specified collection.
*/
public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) {
return new UnmodifiableCollection<>(c);
}
/**
* @serial include
*/
static class UnmodifiableCollection<E> implements Collection<E>, Serializable {
private static final long serialVersionUID = 1820017752578914078L;
final Collection<? extends E> c;
UnmodifiableCollection(Collection<? extends E> c) {
if (c==null)
throw new NullPointerException();
this.c = c;
}
public int size() {return c.size();}
public boolean isEmpty() {return c.isEmpty();}
public boolean contains(Object o) {return c.contains(o);}
public Object[] toArray() {return c.toArray();}
public <T> T[] toArray(T[] a) {return c.toArray(a);}
public String toString() {return c.toString();}
public Iterator<E> iterator() {
return new Iterator<E>() {
private final Iterator<? extends E> i = c.iterator();
public boolean hasNext() {return i.hasNext();}
public E next() {return i.next();}
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public void forEachRemaining(Consumer<? super E> action) {
// Use backing collection version
i.forEachRemaining(action);
}
};
}
public boolean add(E e) {
throw new UnsupportedOperationException();
}
public boolean remove(Object o) {
throw new UnsupportedOperationException();
}
public boolean containsAll(Collection<?> coll) {
return c.containsAll(coll);
}
public boolean addAll(Collection<? extends E> coll) {
throw new UnsupportedOperationException();
}
public boolean removeAll(Collection<?> coll) {
throw new UnsupportedOperationException();
}
public boolean retainAll(Collection<?> coll) {
throw new UnsupportedOperationException();
}
public void clear() {
throw new UnsupportedOperationException();
}
// Override default methods in Collection
@Override
public void forEach(Consumer<? super E> action) {
c.forEach(action);
}
@Override
public boolean removeIf(Predicate<? super E> filter) {
throw new UnsupportedOperationException();
}
@SuppressWarnings("unchecked")
@Override
public Spliterator<E> spliterator() {
return (Spliterator<E>)c.spliterator();
}
@SuppressWarnings("unchecked")
@Override
public Stream<E> stream() {
return (Stream<E>)c.stream();
}
@SuppressWarnings("unchecked")
@Override
public Stream<E> parallelStream() {
return (Stream<E>)c.parallelStream();
}
}
/**
* Returns an unmodifiable view of the specified set. This method allows
* modules to provide users with "read-only" access to internal sets.
* Query operations on the returned set "read through" to the specified
* set, and attempts to modify the returned set, whether direct or via its
* iterator, result in an <tt>UnsupportedOperationException</tt>.<p>
*
* The returned set will be serializable if the specified set
* is serializable.
*
* @param <T> the class of the objects in the set
* @param s the set for which an unmodifiable view is to be returned.
* @return an unmodifiable view of the specified set.
*/
public static <T> Set<T> unmodifiableSet(Set<? extends T> s) {
return new UnmodifiableSet<>(s);
}
/**
* @serial include
*/
static class UnmodifiableSet<E> extends UnmodifiableCollection<E>
implements Set<E>, Serializable {
private static final long serialVersionUID = -9215047833775013803L;
UnmodifiableSet(Set<? extends E> s) {super(s);}
public boolean equals(Object o) {return o == this || c.equals(o);}
public int hashCode() {return c.hashCode();}
}
/**
* Returns an unmodifiable view of the specified sorted set. This method
* allows modules to provide users with "read-only" access to internal
* sorted sets. Query operations on the returned sorted set "read
* through" to the specified sorted set. Attempts to modify the returned
* sorted set, whether direct, via its iterator, or via its
* <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in
* an <tt>UnsupportedOperationException</tt>.<p>
*
* The returned sorted set will be serializable if the specified sorted set
* is serializable.
*
* @param <T> the class of the objects in the set
* @param s the sorted set for which an unmodifiable view is to be
* returned.
* @return an unmodifiable view of the specified sorted set.
*/
public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) {
return new UnmodifiableSortedSet<>(s);
}
/**
* @serial include
*/
static class UnmodifiableSortedSet<E>
extends UnmodifiableSet<E>
implements SortedSet<E>, Serializable {
private static final long serialVersionUID = -4929149591599911165L;
private final SortedSet<E> ss;
UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;}
public Comparator<? super E> comparator() {return ss.comparator();}
public SortedSet<E> subSet(E fromElement, E toElement) {
return new UnmodifiableSortedSet<>(ss.subSet(fromElement,toElement));
}
public SortedSet<E> headSet(E toElement) {
return new UnmodifiableSortedSet<>(ss.headSet(toElement));
}
public SortedSet<E> tailSet(E fromElement) {
return new UnmodifiableSortedSet<>(ss.tailSet(fromElement));
}
public E first() {return ss.first();}
public E last() {return ss.last();}
}
/**
* Returns an unmodifiable view of the specified navigable set. This method
* allows modules to provide users with "read-only" access to internal
* navigable sets. Query operations on the returned navigable set "read
* through" to the specified navigable set. Attempts to modify the returned
* navigable set, whether direct, via its iterator, or via its
* {@code subSet}, {@code headSet}, or {@code tailSet} views, result in
* an {@code UnsupportedOperationException}.<p>
*
* The returned navigable set will be serializable if the specified
* navigable set is serializable.
*
* @param <T> the class of the objects in the set
* @param s the navigable set for which an unmodifiable view is to be
* returned
* @return an unmodifiable view of the specified navigable set
* @since 1.8
*/
public static <T> NavigableSet<T> unmodifiableNavigableSet(NavigableSet<T> s) {
return new UnmodifiableNavigableSet<>(s);
}
/**
* Wraps a navigable set and disables all of the mutative operations.
*
* @param <E> type of elements
* @serial include
*/
static class UnmodifiableNavigableSet<E>
extends UnmodifiableSortedSet<E>
implements NavigableSet<E>, Serializable {
private static final long serialVersionUID = -6027448201786391929L;
/**
* A singleton empty unmodifiable navigable set used for
* {@link #emptyNavigableSet()}.
*
* @param <E> type of elements, if there were any, and bounds
*/
private static class EmptyNavigableSet<E> extends UnmodifiableNavigableSet<E>
implements Serializable {
private static final long serialVersionUID = -6291252904449939134L;
public EmptyNavigableSet() {
super(new TreeSet<E>());
}
private Object readResolve() { return EMPTY_NAVIGABLE_SET; }
}
@SuppressWarnings("rawtypes")
private static final NavigableSet<?> EMPTY_NAVIGABLE_SET =
new EmptyNavigableSet<>();
/**
* The instance we are protecting.
*/
private final NavigableSet<E> ns;
UnmodifiableNavigableSet(NavigableSet<E> s) {super(s); ns = s;}
public E lower(E e) { return ns.lower(e); }
public E floor(E e) { return ns.floor(e); }
public E ceiling(E e) { return ns.ceiling(e); }
public E higher(E e) { return ns.higher(e); }
public E pollFirst() { throw new UnsupportedOperationException(); }
public E pollLast() { throw new UnsupportedOperationException(); }
public NavigableSet<E> descendingSet()
{ return new UnmodifiableNavigableSet<>(ns.descendingSet()); }
public Iterator<E> descendingIterator()
{ return descendingSet().iterator(); }
public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
return new UnmodifiableNavigableSet<>(
ns.subSet(fromElement, fromInclusive, toElement, toInclusive));
}
public NavigableSet<E> headSet(E toElement, boolean inclusive) {
return new UnmodifiableNavigableSet<>(
ns.headSet(toElement, inclusive));
}
public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
return new UnmodifiableNavigableSet<>(
ns.tailSet(fromElement, inclusive));
}
}
/**
* Returns an unmodifiable view of the specified list. This method allows
* modules to provide users with "read-only" access to internal
* lists. Query operations on the returned list "read through" to the
* specified list, and attempts to modify the returned list, whether
* direct or via its iterator, result in an
* <tt>UnsupportedOperationException</tt>.<p>
*
* The returned list will be serializable if the specified list
* is serializable. Similarly, the returned list will implement
* {@link RandomAccess} if the specified list does.
*
* @param <T> the class of the objects in the list
* @param list the list for which an unmodifiable view is to be returned.
* @return an unmodifiable view of the specified list.
*/
public static <T> List<T> unmodifiableList(List<? extends T> list) {
return (list instanceof RandomAccess ?
new UnmodifiableRandomAccessList<>(list) :
new UnmodifiableList<>(list));
}
/**
* @serial include
*/
static class UnmodifiableList<E> extends UnmodifiableCollection<E>
implements List<E> {
private static final long serialVersionUID = -283967356065247728L;
final List<? extends E> list;
UnmodifiableList(List<? extends E> list) {
super(list);
this.list = list;
}
public boolean equals(Object o) {return o == this || list.equals(o);}
public int hashCode() {return list.hashCode();}
public E get(int index) {return list.get(index);}
public E set(int index, E element) {
throw new UnsupportedOperationException();
}
public void add(int index, E element) {
throw new UnsupportedOperationException();
}
public E remove(int index) {
throw new UnsupportedOperationException();
}
public int indexOf(Object o) {return list.indexOf(o);}
public int lastIndexOf(Object o) {return list.lastIndexOf(o);}
public boolean addAll(int index, Collection<? extends E> c) {
throw new UnsupportedOperationException();
}
@Override
public void replaceAll(UnaryOperator<E> operator) {
throw new UnsupportedOperationException();
}
@Override
public void sort(Comparator<? super E> c) {
throw new UnsupportedOperationException();
}
public ListIterator<E> listIterator() {return listIterator(0);}
public ListIterator<E> listIterator(final int index) {
return new ListIterator<E>() {
private final ListIterator<? extends E> i
= list.listIterator(index);
public boolean hasNext() {return i.hasNext();}
public E next() {return i.next();}
public boolean hasPrevious() {return i.hasPrevious();}
public E previous() {return i.previous();}
public int nextIndex() {return i.nextIndex();}
public int previousIndex() {return i.previousIndex();}
public void remove() {
throw new UnsupportedOperationException();
}
public void set(E e) {
throw new UnsupportedOperationException();
}
public void add(E e) {
throw new UnsupportedOperationException();
}
@Override
public void forEachRemaining(Consumer<? super E> action) {
i.forEachRemaining(action);
}
};
}
public List<E> subList(int fromIndex, int toIndex) {
return new UnmodifiableList<>(list.subList(fromIndex, toIndex));
}
/**
* UnmodifiableRandomAccessList instances are serialized as
* UnmodifiableList instances to allow them to be deserialized
* in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList).
* This method inverts the transformation. As a beneficial
* side-effect, it also grafts the RandomAccess marker onto
* UnmodifiableList instances that were serialized in pre-1.4 JREs.
*
* Note: Unfortunately, UnmodifiableRandomAccessList instances
* serialized in 1.4.1 and deserialized in 1.4 will become
* UnmodifiableList instances, as this method was missing in 1.4.
*/
private Object readResolve() {
return (list instanceof RandomAccess
? new UnmodifiableRandomAccessList<>(list)
: this);
}
}
/**
* @serial include
*/
static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E>
implements RandomAccess
{
UnmodifiableRandomAccessList(List<? extends E> list) {
super(list);
}
public List<E> subList(int fromIndex, int toIndex) {
return new UnmodifiableRandomAccessList<>(
list.subList(fromIndex, toIndex));
}
private static final long serialVersionUID = -2542308836966382001L;
/**
* Allows instances to be deserialized in pre-1.4 JREs (which do
* not have UnmodifiableRandomAccessList). UnmodifiableList has
* a readResolve method that inverts this transformation upon
* deserialization.
*/
private Object writeReplace() {
return new UnmodifiableList<>(list);
}
}
/**
* Returns an unmodifiable view of the specified map. This method
* allows modules to provide users with "read-only" access to internal
* maps. Query operations on the returned map "read through"
* to the specified map, and attempts to modify the returned
* map, whether direct or via its collection views, result in an
* <tt>UnsupportedOperationException</tt>.<p>
*
* The returned map will be serializable if the specified map
* is serializable.
*
* @param <K> the class of the map keys
* @param <V> the class of the map values
* @param m the map for which an unmodifiable view is to be returned.
* @return an unmodifiable view of the specified map.
*/
public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) {
return new UnmodifiableMap<>(m);
}
/**
* @serial include
*/
private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable {
private static final long serialVersionUID = -1034234728574286014L;
private final Map<? extends K, ? extends V> m;
UnmodifiableMap(Map<? extends K, ? extends V> m) {
if (m==null)
throw new NullPointerException();
this.m = m;
}
public int size() {return m.size();}
public boolean isEmpty() {return m.isEmpty();}
public boolean containsKey(Object key) {return m.containsKey(key);}
public boolean containsValue(Object val) {return m.containsValue(val);}
public V get(Object key) {return m.get(key);}
public V put(K key, V value) {
throw new UnsupportedOperationException();
}
public V remove(Object key) {
throw new UnsupportedOperationException();
}
public void putAll(Map<? extends K, ? extends V> m) {
throw new UnsupportedOperationException();
}
public void clear() {
throw new UnsupportedOperationException();
}
private transient Set<K> keySet;
private transient Set<Map.Entry<K,V>> entrySet;
private transient Collection<V> values;
public Set<K> keySet() {
if (keySet==null)
keySet = unmodifiableSet(m.keySet());
return keySet;
}
public Set<Map.Entry<K,V>> entrySet() {
if (entrySet==null)
entrySet = new UnmodifiableEntrySet<>(m.entrySet());
return entrySet;
}
public Collection<V> values() {
if (values==null)
values = unmodifiableCollection(m.values());
return values;
}
public boolean equals(Object o) {return o == this || m.equals(o);}
public int hashCode() {return m.hashCode();}
public String toString() {return m.toString();}
// Override default methods in Map
@Override
@SuppressWarnings("unchecked")
public V getOrDefault(Object k, V defaultValue) {
// Safe cast as we don't change the value
return ((Map<K, V>)m).getOrDefault(k, defaultValue);
}
@Override
public void forEach(BiConsumer<? super K, ? super V> action) {
m.forEach(action);
}
@Override
public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
throw new UnsupportedOperationException();
}
@Override
public V putIfAbsent(K key, V value) {
throw new UnsupportedOperationException();
}
@Override
public boolean remove(Object key, Object value) {
throw new UnsupportedOperationException();
}
@Override
public boolean replace(K key, V oldValue, V newValue) {
throw new UnsupportedOperationException();
}
@Override
public V replace(K key, V value) {
throw new UnsupportedOperationException();
}
@Override
public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V computeIfPresent(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V compute(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
@Override
public V merge(K key, V value,
BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
throw new UnsupportedOperationException();
}
/**
* We need this class in addition to UnmodifiableSet as
* Map.Entries themselves permit modification of the backing Map
* via their setValue operation. This class is subtle: there are
* many possible attacks that must be thwarted.
*
* @serial include
*/
static class UnmodifiableEntrySet<K,V>
extends UnmodifiableSet<Map.Entry<K,V>> {
private static final long serialVersionUID = 7854390611657943733L;
@SuppressWarnings({"unchecked", "rawtypes"})
UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) {
// Need to cast to raw in order to work around a limitation in the type system
super((Set)s);
}
static <K, V> Consumer<Map.Entry<K, V>> entryConsumer(Consumer<? super Entry<K, V>> action) {
return e -> action.accept(new UnmodifiableEntry<>(e));
}
public void forEach(Consumer<? super Entry<K, V>> action) {
Objects.requireNonNull(action);
c.forEach(entryConsumer(action));
}
static final class UnmodifiableEntrySetSpliterator<K, V>
implements Spliterator<Entry<K,V>> {
final Spliterator<Map.Entry<K, V>> s;
UnmodifiableEntrySetSpliterator(Spliterator<Entry<K, V>> s) {
this.s = s;
}
@Override
public boolean tryAdvance(Consumer<? super Entry<K, V>> action) {
Objects.requireNonNull(action);
return s.tryAdvance(entryConsumer(action));
}
@Override
public void forEachRemaining(Consumer<? super Entry<K, V>> action) {
Objects.requireNonNull(action);
s.forEachRemaining(entryConsumer(action));
}
@Override
public Spliterator<Entry<K, V>> trySplit() {
Spliterator<Entry<K, V>> split = s.trySplit();
return split == null
? null
: new UnmodifiableEntrySetSpliterator<>(split);
}
@Override
public long estimateSize() {
return s.estimateSize();
}
@Override
public long getExactSizeIfKnown() {
return s.getExactSizeIfKnown();
}
@Override
public int characteristics() {
return s.characteristics();
}
@Override
public boolean hasCharacteristics(int characteristics) {
return s.hasCharacteristics(characteristics);
}
@Override
public Comparator<? super Entry<K, V>> getComparator() {
return s.getComparator();
}
}
@SuppressWarnings("unchecked")
public Spliterator<Entry<K,V>> spliterator() {
return new UnmodifiableEntrySetSpliterator<>(
(Spliterator<Map.Entry<K, V>>) c.spliterator());
}
@Override
public Stream<Entry<K,V>> stream() {
return StreamSupport.stream(spliterator(), false);
}
@Override
public Stream<Entry<K,V>> parallelStream() {
return StreamSupport.stream(spliterator(), true);
}
public Iterator<Map.Entry<K,V>> iterator() {
return new Iterator<Map.Entry<K,V>>() {
private final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator();
public boolean hasNext() {
return i.hasNext();
}
public Map.Entry<K,V> next() {
return new UnmodifiableEntry<>(i.next());
}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
@SuppressWarnings("unchecked")
public Object[] toArray() {
Object[] a = c.toArray();
for (int i=0; i<a.length; i++)
a[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)a[i]);
return a;
}
@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) {
// We don't pass a to c.toArray, to avoid window of
// vulnerability wherein an unscrupulous multithreaded client
// could get his hands on raw (unwrapped) Entries from c.
Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
for (int i=0; i<arr.length; i++)
arr[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)arr[i]);
if (arr.length > a.length)
return (T[])arr;
System.arraycopy(arr, 0, a, 0, arr.length);
if (a.length > arr.length)
a[arr.length] = null;
return a;
}
/**
* This method is overridden to protect the backing set against
* an object with a nefarious equals function that senses
* that the equality-candidate is Map.Entry and calls its
* setValue method.
*/
public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
return c.contains(
new UnmodifiableEntry<>((Map.Entry<?,?>) o));
}
/**
* The next two methods are overridden to protect against
* an unscrupulous List whose contains(Object o) method senses
* when o is a Map.Entry, and calls o.setValue.
*/
public boolean containsAll(Collection<?> coll) {
for (Object e : coll) {
if (!contains(e)) // Invokes safe contains() above
return false;
}
return true;
}
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof Set))
return false;
Set<?> s = (Set<?>) o;
if (s.size() != c.size())
return false;
return containsAll(s); // Invokes safe containsAll() above
}
/**
* This "wrapper class" serves two purposes: it prevents
* the client from modifying the backing Map, by short-circuiting
* the setValue method, and it protects the backing Map against
* an ill-behaved Map.Entry that attempts to modify another
* Map Entry when asked to perform an equality check.
*/
private static class UnmodifiableEntry<K,V> implements Map.Entry<K,V> {
private Map.Entry<? extends K, ? extends V> e;
UnmodifiableEntry(Map.Entry<? extends K, ? extends V> e)
{this.e = Objects.requireNonNull(e);}
public K getKey() {return e.getKey();}
public V getValue() {return e.getValue();}
public V setValue(V value) {
throw new UnsupportedOperationException();
}
public int hashCode() {return e.hashCode();}
public boolean equals(Object o) {
if (this == o)
return true;
if (!(o instanceof Map.Entry))
return false;
Map.Entry<?,?> t = (Map.Entry<?,?>)o;
return eq(e.getKey(), t.getKey()) &&
eq(e.getValue(), t.getValue());
}
public String toString() {return e.toString();}
}
}
}
/**
* Returns an unmodifiable view of the specified sorted map. This method
* allows modules to provide users with "read-only" access to internal
* sorted maps. Query operations on the returned sorted map "read through"
* to the specified sorted map. Attempts to modify the returned
* sorted map, whether direct, via its collection views, or via its
* <tt>subMap</tt>, <tt>headMap</tt>, or <tt>tailMap</tt> views, result in
* an <tt>UnsupportedOperationException</tt>.<p>
*
* The returned sorted map will be serializable if the specified sorted map
* is serializable.
*
* @param <K> the class of the map keys
* @param <V> the class of the map values
* @param m the sorted map for which an unmodifiable view is to be
* returned.
* @return an unmodifiable view of the specified sorted map.
*/
public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) {
return new UnmodifiableSortedMap<>(m);
}
/**
* @serial include
*/
static class UnmodifiableSortedMap<K,V>
extends UnmodifiableMap<K,V>
implements SortedMap<K,V>, Serializable {
private static final long serialVersionUID = -8806743815996713206L;
private final SortedMap<K, ? extends V> sm;
UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m; }
public Comparator<? super K> comparator() { return sm.comparator(); }
public SortedMap<K,V> subMap(K fromKey, K toKey)
{ return new UnmodifiableSortedMap<>(sm.subMap(fromKey, toKey)); }
public SortedMap<K,V> headMap(K toKey)
{ return new UnmodifiableSortedMap<>(sm.headMap(toKey)); }
public SortedMap<K,V> tailMap(K fromKey)
{ return new UnmodifiableSortedMap<>(sm.tailMap(fromKey)); }
public K firstKey() { return sm.firstKey(); }
public K lastKey() { return sm.lastKey(); }
}
/**
* Returns an unmodifiable view of the specified navigable map. This method
* allows modules to provide users with "read-only" access to internal
* navigable maps. Query operations on the returned navigable map "read
* through" to the specified navigable map. Attempts to modify the returned
* navigable map, whether direct, via its collection views, or via its
* {@code subMap}, {@code headMap}, or {@code tailMap} views, result in
* an {@code UnsupportedOperationException}.<p>
*
* The returned navigable map will be serializable if the specified
* navigable map is serializable.
*
* @param <K> the class of the map keys
* @param <V> the class of the map values
* @param m the navigable map for which an unmodifiable view is to be
* returned
* @return an unmodifiable view of the specified navigable map
* @since 1.8
*/
public static <K,V> NavigableMap<K,V> unmodifiableNavigableMap(NavigableMap<K, ? extends V> m) {
return new UnmodifiableNavigableMap<>(m);
}
/**
* @serial include
*/
static class UnmodifiableNavigableMap<K,V>
extends UnmodifiableSortedMap<K,V>
implements NavigableMap<K,V>, Serializable {
private static final long serialVersionUID = -4858195264774772197L;
/**
* A class for the {@link EMPTY_NAVIGABLE_MAP} which needs readResolve
* to preserve singleton property.
*
* @param <K> type of keys, if there were any, and of bounds
* @param <V> type of values, if there were any
*/
private static class EmptyNavigableMap<K,V> extends UnmodifiableNavigableMap<K,V>
implements Serializable {
private static final long serialVersionUID = -2239321462712562324L;
EmptyNavigableMap() { super(new TreeMap<K,V>()); }
@Override
public NavigableSet<K> navigableKeySet()
{ return emptyNavigableSet(); }
private Object readResolve() { return EMPTY_NAVIGABLE_MAP; }
}
/**
* Singleton for {@link emptyNavigableMap()} which is also immutable.
*/
private static final EmptyNavigableMap<?,?> EMPTY_NAVIGABLE_MAP =
new EmptyNavigableMap<>();
/**
* The instance we wrap and protect.
*/
private final NavigableMap<K, ? extends V> nm;
UnmodifiableNavigableMap(NavigableMap<K, ? extends V> m)
{super(m); nm = m;}
public K lowerKey(K key) { return nm.lowerKey(key); }
public K floorKey(K key) { return nm.floorKey(key); }
public K ceilingKey(K key) { return nm.ceilingKey(key); }
public K higherKey(K key) { return nm.higherKey(key); }
@SuppressWarnings("unchecked")
public Entry<K, V> lowerEntry(K key) {
Entry<K,V> lower = (Entry<K, V>) nm.lowerEntry(key);
return (null != lower)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(lower)
: null;
}
@SuppressWarnings("unchecked")
public Entry<K, V> floorEntry(K key) {
Entry<K,V> floor = (Entry<K, V>) nm.floorEntry(key);
return (null != floor)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(floor)
: null;
}
@SuppressWarnings("unchecked")
public Entry<K, V> ceilingEntry(K key) {
Entry<K,V> ceiling = (Entry<K, V>) nm.ceilingEntry(key);
return (null != ceiling)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(ceiling)
: null;
}
@SuppressWarnings("unchecked")
public Entry<K, V> higherEntry(K key) {
Entry<K,V> higher = (Entry<K, V>) nm.higherEntry(key);
return (null != higher)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(higher)
: null;
}
@SuppressWarnings("unchecked")
public Entry<K, V> firstEntry() {
Entry<K,V> first = (Entry<K, V>) nm.firstEntry();
return (null != first)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(first)
: null;
}
@SuppressWarnings("unchecked")
public Entry<K, V> lastEntry() {
Entry<K,V> last = (Entry<K, V>) nm.lastEntry();
return (null != last)
? new UnmodifiableEntrySet.UnmodifiableEntry<>(last)
: null;
}
public Entry<K, V> pollFirstEntry()
{ throw new UnsupportedOperationException(); }
public Entry<K, V> pollLastEntry()
{ throw new UnsupportedOperationException(); }
public NavigableMap<K, V> descendingMap()
{ return unmodifiableNavigableMap(nm.descendingMap()); }
public NavigableSet<K> navigableKeySet()
{ return unmodifiableNavigableSet(nm.navigableKeySet()); }
public NavigableSet<K> descendingKeySet()
{ return unmodifiableNavigableSet(nm.descendingKeySet()); }
public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
return unmodifiableNavigableMap(
nm.subMap(fromKey, fromInclusive, toKey, toInclusive));
}
public NavigableMap<K, V> headMap(K toKey, boolean inclusive)
{ return unmodifiableNavigableMap(nm.headMap(toKey, inclusive)); }
public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive)
{ return unmodifiableNavigableMap(nm.tailMap(fromKey, inclusive)); }
}
// Synch Wrappers
/**
* Returns a synchronized (thread-safe) collection backed by the specified
* collection. In order to guarantee serial access, it is critical that
* <strong>all</strong> access to the backing collection is accomplished
* through the returned collection.<p>
*
* It is imperative that the user manually synchronize on the returned
* collection when traversing it via {@link Iterator}, {@link Spliterator}
* or {@link Stream}:
* <pre>
* Collection c = Collections.synchronizedCollection(myCollection);
* ...
* synchronized (c) {
* Iterator i = c.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
* </pre>
* Failure to follow this advice may result in non-deterministic behavior.
*
* <p>The returned collection does <i>not</i> pass the {@code hashCode}
* and {@code equals} operations through to the backing collection, but
* relies on {@code Object}'s equals and hashCode methods. This is
* necessary to preserve the contracts of these operations in the case
* that the backing collection is a set or a list.<p>
*
* The returned collection will be serializable if the specified collection
* is serializable.
*
* @param <T> the class of the objects in the collection
* @param c the collection to be "wrapped" in a synchronized collection.
* @return a synchronized view of the specified collection.
*/
public static <T> Collection<T> synchronizedCollection(Collection<T> c) {
return new SynchronizedCollection<>(c);
}
static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) {
return new SynchronizedCollection<>(c, mutex);
}
/**
* @serial include
*/
static class SynchronizedCollection<E> implements Collection<E>, Serializable {
private static final long serialVersionUID = 3053995032091335093L;
final Collection<E> c; // Backing Collection
final Object mutex; // Object on which to synchronize
SynchronizedCollection(Collection<E> c) {
this.c = Objects.requireNonNull(c);
mutex = this;
}
SynchronizedCollection(Collection<E> c, Object mutex) {
this.c = Objects.requireNonNull(c);
this.mutex = Objects.requireNonNull(mutex);
}
public int size() {
synchronized (mutex) {return c.size();}
}
public boolean isEmpty() {
synchronized (mutex) {return c.isEmpty();}
}
public boolean contains(Object o) {
synchronized (mutex) {return c.contains(o);}
}
public Object[] toArray() {
synchronized (mutex) {return c.toArray();}
}
public <T> T[] toArray(T[] a) {
synchronized (mutex) {return c.toArray(a);}
}
public Iterator<E> iterator() {
return c.iterator(); // Must be manually synched by user!
}
public boolean add(E e) {
synchronized (mutex) {return c.add(e);}
}
public boolean remove(Object o) {
synchronized (mutex) {return c.remove(o);}
}
public boolean containsAll(Collection<?> coll) {
synchronized (mutex) {return c.containsAll(coll);}
}
public boolean addAll(Collection<? extends E> coll) {
synchronized (mutex) {return c.addAll(coll);}
}
public boolean removeAll(Collection<?> coll) {
synchronized (mutex) {return c.removeAll(coll);}
}
public boolean retainAll(Collection<?> coll) {
synchronized (mutex) {return c.retainAll(coll);}
}
public void clear() {
synchronized (mutex) {c.clear();}
}
public String toString() {
synchronized (mutex) {return c.toString();}
}
// Override default methods in Collection
@Override
public void forEach(Consumer<? super E> consumer) {
synchronized (mutex) {c.forEach(consumer);}
}
@Override
public boolean removeIf(Predicate<? super E> filter) {
synchronized (mutex) {return c.removeIf(filter);}
}
@Override
public Spliterator<E> spliterator() {
return c.spliterator(); // Must be manually synched by user!
}
@Override
public Stream<E> stream() {
return c.stream(); // Must be manually synched by user!
}
@Override
public Stream<E> parallelStream() {
return c.parallelStream(); // Must be manually synched by user!
}
private void writeObject(ObjectOutputStream s) throws IOException {
synchronized (mutex) {s.defaultWriteObject();}
}
}
/**
* Returns a synchronized (thread-safe) set backed by the specified
* set. In order to guarantee serial access, it is critical that
* <strong>all</strong> access to the backing set is accomplished
* through the returned set.<p>
*
* It is imperative that the user manually synchronize on the returned
* set when iterating over it:
* <pre>
* Set s = Collections.synchronizedSet(new HashSet());
* ...
* synchronized (s) {
* Iterator i = s.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
* </pre>
* Failure to follow this advice may result in non-deterministic behavior.
*
* <p>The returned set will be serializable if the specified set is
* serializable.
*
* @param <T> the class of the objects in the set
* @param s the set to be "wrapped" in a synchronized set.
* @return a synchronized view of the specified set.
*/
public static <T> Set<T> synchronizedSet(Set<T> s) {
return new SynchronizedSet<>(s);
}
static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) {
return new SynchronizedSet<>(s, mutex);
}
/**
* @serial include
*/
static class SynchronizedSet<E>
extends SynchronizedCollection<E>
implements Set<E> {
private static final long serialVersionUID = 487447009682186044L;
SynchronizedSet(Set<E> s) {
super(s);
}
SynchronizedSet(Set<E> s, Object mutex) {
super(s, mutex);
}
public boolean equals(Object o) {
if (this == o)
return true;
synchronized (mutex) {return c.equals(o);}
}
public int hashCode() {
synchronized (mutex) {return c.hashCode();}
}
}
/**
* Returns a synchronized (thread-safe) sorted set backed by the specified
* sorted set. In order to guarantee serial access, it is critical that
* <strong>all</strong> access to the backing sorted set is accomplished
* through the returned sorted set (or its views).<p>
*
* It is imperative that the user manually synchronize on the returned
* sorted set when iterating over it or any of its <tt>subSet</tt>,
* <tt>headSet</tt>, or <tt>tailSet</tt> views.
* <pre>
* SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
* ...
* synchronized (s) {
* Iterator i = s.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
* </pre>
* or:
* <pre>
* SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
* SortedSet s2 = s.headSet(foo);
* ...
* synchronized (s) { // Note: s, not s2!!!
* Iterator i = s2.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
* </pre>
* Failure to follow this advice may result in non-deterministic behavior.
*
* <p>The returned sorted set will be serializable if the specified
* sorted set is serializable.
*
* @param <T> the class of the objects in the set
* @param s the sorted set to be "wrapped" in a synchronized sorted set.
* @return a synchronized view of the specified sorted set.
*/
public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) {
return new SynchronizedSortedSet<>(s);
}
/**
* @serial include
*/
static class SynchronizedSortedSet<E>
extends SynchronizedSet<E>
implements SortedSet<E>
{
private static final long serialVersionUID = 8695801310862127406L;
private final SortedSet<E> ss;
SynchronizedSortedSet(SortedSet<E> s) {
super(s);
ss = s;
}
SynchronizedSortedSet(SortedSet<E> s, Object mutex) {
super(s, mutex);
ss = s;
}
public Comparator<? super E> comparator() {
synchronized (mutex) {return ss.comparator();}
}
public SortedSet<E> subSet(E fromElement, E toElement) {
synchronized (mutex) {
return new SynchronizedSortedSet<>(
ss.subSet(fromElement, toElement), mutex);
}
}
public SortedSet<E> headSet(E toElement) {
synchronized (mutex) {
return new SynchronizedSortedSet<>(ss.headSet(toElement), mutex);
}
}
public SortedSet<E> tailSet(E fromElement) {
synchronized (mutex) {
return new SynchronizedSortedSet<>(ss.tailSet(fromElement),mutex);
}
}
public E first() {
synchronized (mutex) {return ss.first();}
}
public E last() {
synchronized (mutex) {return ss.last();}
}
}
/**
* Returns a synchronized (thread-safe) navigable set backed by the
* specified navigable set. In order to guarantee serial access, it is
* critical that <strong>all</strong> access to the backing navigable set is
* accomplished through the returned navigable set (or its views).<p>
*
* It is imperative that the user manually synchronize on the returned
* navigable set when iterating over it or any of its {@code subSet},
* {@code headSet}, or {@code tailSet} views.
* <pre>
* NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet());
* ...
* synchronized (s) {
* Iterator i = s.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
* </pre>
* or:
* <pre>
* NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet());
* NavigableSet s2 = s.headSet(foo, true);
* ...
* synchronized (s) { // Note: s, not s2!!!
* Iterator i = s2.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
* </pre>
* Failure to follow this advice may result in non-deterministic behavior.
*
* <p>The returned navigable set will be serializable if the specified
* navigable set is serializable.
*
* @param <T> the class of the objects in the set
* @param s the navigable set to be "wrapped" in a synchronized navigable
* set
* @return a synchronized view of the specified navigable set
* @since 1.8
*/
public static <T> NavigableSet<T> synchronizedNavigableSet(NavigableSet<T> s) {
return new SynchronizedNavigableSet<>(s);
}
/**
* @serial include
*/
static class SynchronizedNavigableSet<E>
extends SynchronizedSortedSet<E>
implements NavigableSet<E>
{
private static final long serialVersionUID = -5505529816273629798L;
private final NavigableSet<E> ns;
SynchronizedNavigableSet(NavigableSet<E> s) {
super(s);
ns = s;
}
SynchronizedNavigableSet(NavigableSet<E> s, Object mutex) {
super(s, mutex);
ns = s;
}
public E lower(E e) { synchronized (mutex) {return ns.lower(e);} }
public E floor(E e) { synchronized (mutex) {return ns.floor(e);} }
public E ceiling(E e) { synchronized (mutex) {return ns.ceiling(e);} }
public E higher(E e) { synchronized (mutex) {return ns.higher(e);} }
public E pollFirst() { synchronized (mutex) {return ns.pollFirst();} }
public E pollLast() { synchronized (mutex) {return ns.pollLast();} }
public NavigableSet<E> descendingSet() {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.descendingSet(), mutex);
}
}
public Iterator<E> descendingIterator()
{ synchronized (mutex) { return descendingSet().iterator(); } }
public NavigableSet<E> subSet(E fromElement, E toElement) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.subSet(fromElement, true, toElement, false), mutex);
}
}
public NavigableSet<E> headSet(E toElement) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.headSet(toElement, false), mutex);
}
}
public NavigableSet<E> tailSet(E fromElement) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, true), mutex);
}
}
public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), mutex);
}
}
public NavigableSet<E> headSet(E toElement, boolean inclusive) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.headSet(toElement, inclusive), mutex);
}
}
public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, inclusive), mutex);
}
}
}
/**
* Returns a synchronized (thread-safe) list backed by the specified
* list. In order to guarantee serial access, it is critical that
* <strong>all</strong> access to the backing list is accomplished
* through the returned list.<p>
*
* It is imperative that the user manually synchronize on the returned
* list when iterating over it:
* <pre>
* List list = Collections.synchronizedList(new ArrayList());
* ...
* synchronized (list) {
* Iterator i = list.iterator(); // Must be in synchronized block
* while (i.hasNext())
* foo(i.next());
* }
* </pre>
* Failure to follow this advice may result in non-deterministic behavior.
*
* <p>The returned list will be serializable if the specified list is
* serializable.
*
* @param <T> the class of the objects in the list
* @param list the list to be "wrapped" in a synchronized list.
* @return a synchronized view of the specified list.
*/
public static <T> List<T> synchronizedList(List<T> list) {
return (list instanceof RandomAccess ?
new SynchronizedRandomAccessList<>(list) :
new SynchronizedList<>(list));
}
static <T> List<T> synchronizedList(List<T> list, Object mutex) {
return (list instanceof RandomAccess ?
new SynchronizedRandomAccessList<>(list, mutex) :
new SynchronizedList<>(list, mutex));
}
/**
* @serial include
*/
static class SynchronizedList<E>
extends SynchronizedCollection<E>
implements List<E> {
private static final long serialVersionUID = -7754090372962971524L;
final List<E> list;
SynchronizedList(List<E> list) {
super(list);
this.list = list;
}
SynchronizedList(List<E> list, Object mutex) {
super(list, mutex);
this.list = list;
}
public boolean equals(Object o) {
if (this == o)
return true;
synchronized (mutex) {return list.equals(o);}
}
public int hashCode() {
synchronized (mutex) {return list.hashCode();}
}
public E get(int index) {
synchronized (mutex) {return list.get(index);}
}
public E set(int index, E element) {
synchronized (mutex) {return list.set(index, element);}
}
public void add(int index, E element) {
synchronized (mutex) {list.add(index, element);}
}
public E remove(int index) {
synchronized (mutex) {return list.remove(index);}
}
public int indexOf(Object o) {
synchronized (mutex) {return list.indexOf(o);}
}
public int lastIndexOf(Object o) {
synchronized (mutex) {return list.lastIndexOf(o);}
}
public boolean addAll(int index, Collection<? extends E> c) {
synchronized (mutex) {return list.addAll(index, c);}
}
public ListIterator<E> listIterator() {
return list.listIterator(); // Must be manually synched by user
}
public ListIterator<E> listIterator(int index) {
return list.listIterator(index); // Must be manually synched by user
}
public List<E> subList(int fromIndex, int toIndex) {
synchronized (mutex) {
return new SynchronizedList<>(list.subList(fromIndex, toIndex),
mutex);
}
}
@Override
public void replaceAll(UnaryOperator<E> operator) {
synchronized (mutex) {list.replaceAll(operator);}
}
@Override
public void sort(Comparator<? super E> c) {
synchronized (mutex) {list.sort(c);}
}
/**
* SynchronizedRandomAccessList instances are serialized as
* SynchronizedList instances to allow them to be deserialized
* in pre-1.4 JREs (which do not have SynchronizedRandomAccessList).
* This method inverts the transformation. As a beneficial
* side-effect, it also grafts the RandomAccess marker onto
* SynchronizedList instances that were serialized in pre-1.4 JREs.
*
* Note: Unfortunately, SynchronizedRandomAccessList instances
* serialized in 1.4.1 and deserialized in 1.4 will become
* SynchronizedList instances, as this method was missing in 1.4.
*/
private Object readResolve() {
return (list instanceof RandomAccess
? new SynchronizedRandomAccessList<>(list)
: this);
}
}
/**
* @serial include
*/
static class SynchronizedRandomAccessList<E>
extends SynchronizedList<E>
implements RandomAccess {
SynchronizedRandomAccessList(List<E> list) {
super(list);
}
SynchronizedRandomAccessList(List<E> list, Object mutex) {
super(list, mutex);
}
public List<E> subList(int fromIndex, int toIndex) {
synchronized (mutex) {
return new SynchronizedRandomAccessList<>(
list.subList(fromIndex, toIndex), mutex);
}
}
private static final long serialVersionUID = 1530674583602358482L;
/**
* Allows instances to be deserialized in pre-1.4 JREs (which do
* not have SynchronizedRandomAccessList). SynchronizedList has
* a readResolve method that inverts this transformation upon
* deserialization.
*/
private Object writeReplace() {
return new SynchronizedList<>(list);
}
}
...
}
JDK 工具类之 Collections
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