/**
* Returns a synchronized (thread-safe) map backed by the specified
* map. In order to guarantee serial access, it is critical that
* <strong>all</strong> access to the backing map is accomplished
* through the returned map.<p>
*
* It is imperative that the user manually synchronize on the returned
* map when iterating over any of its collection views:
* <pre>
* Map m = Collections.synchronizedMap(new HashMap());
* ...
* Set s = m.keySet(); // Needn't be in synchronized block
* ...
* synchronized (m) { // Synchronizing on m, not s!
* Iterator i = s.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 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 to be "wrapped" in a synchronized map.
* @return a synchronized view of the specified map.
*/
public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) {
return new SynchronizedMap<>(m);
}
/**
* @serial include
*/
private static class SynchronizedMap<K,V>
implements Map<K,V>, Serializable {
private static final long serialVersionUID = 1978198479659022715L;
private final Map<K,V> m; // Backing Map
final Object mutex; // Object on which to synchronize
SynchronizedMap(Map<K,V> m) {
this.m = Objects.requireNonNull(m);
mutex = this;
}
SynchronizedMap(Map<K,V> m, Object mutex) {
this.m = m;
this.mutex = mutex;
}
public int size() {
synchronized (mutex) {return m.size();}
}
public boolean isEmpty() {
synchronized (mutex) {return m.isEmpty();}
}
public boolean containsKey(Object key) {
synchronized (mutex) {return m.containsKey(key);}
}
public boolean containsValue(Object value) {
synchronized (mutex) {return m.containsValue(value);}
}
public V get(Object key) {
synchronized (mutex) {return m.get(key);}
}
public V put(K key, V value) {
synchronized (mutex) {return m.put(key, value);}
}
public V remove(Object key) {
synchronized (mutex) {return m.remove(key);}
}
public void putAll(Map<? extends K, ? extends V> map) {
synchronized (mutex) {m.putAll(map);}
}
public void clear() {
synchronized (mutex) {m.clear();}
}
private transient Set<K> keySet;
private transient Set<Map.Entry<K,V>> entrySet;
private transient Collection<V> values;
public Set<K> keySet() {
synchronized (mutex) {
if (keySet==null)
keySet = new SynchronizedSet<>(m.keySet(), mutex);
return keySet;
}
}
public Set<Map.Entry<K,V>> entrySet() {
synchronized (mutex) {
if (entrySet==null)
entrySet = new SynchronizedSet<>(m.entrySet(), mutex);
return entrySet;
}
}
public Collection<V> values() {
synchronized (mutex) {
if (values==null)
values = new SynchronizedCollection<>(m.values(), mutex);
return values;
}
}
public boolean equals(Object o) {
if (this == o)
return true;
synchronized (mutex) {return m.equals(o);}
}
public int hashCode() {
synchronized (mutex) {return m.hashCode();}
}
public String toString() {
synchronized (mutex) {return m.toString();}
}
// Override default methods in Map
@Override
public V getOrDefault(Object k, V defaultValue) {
synchronized (mutex) {return m.getOrDefault(k, defaultValue);}
}
@Override
public void forEach(BiConsumer<? super K, ? super V> action) {
synchronized (mutex) {m.forEach(action);}
}
@Override
public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
synchronized (mutex) {m.replaceAll(function);}
}
@Override
public V putIfAbsent(K key, V value) {
synchronized (mutex) {return m.putIfAbsent(key, value);}
}
@Override
public boolean remove(Object key, Object value) {
synchronized (mutex) {return m.remove(key, value);}
}
@Override
public boolean replace(K key, V oldValue, V newValue) {
synchronized (mutex) {return m.replace(key, oldValue, newValue);}
}
@Override
public V replace(K key, V value) {
synchronized (mutex) {return m.replace(key, value);}
}
@Override
public V computeIfAbsent(K key,
Function<? super K, ? extends V> mappingFunction) {
synchronized (mutex) {return m.computeIfAbsent(key, mappingFunction);}
}
@Override
public V computeIfPresent(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
synchronized (mutex) {return m.computeIfPresent(key, remappingFunction);}
}
@Override
public V compute(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
synchronized (mutex) {return m.compute(key, remappingFunction);}
}
@Override
public V merge(K key, V value,
BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
synchronized (mutex) {return m.merge(key, value, remappingFunction);}
}
private void writeObject(ObjectOutputStream s) throws IOException {
synchronized (mutex) {s.defaultWriteObject();}
}
}
/**
* Returns a synchronized (thread-safe) sorted map backed by the specified
* sorted map. In order to guarantee serial access, it is critical that
* <strong>all</strong> access to the backing sorted map is accomplished
* through the returned sorted map (or its views).<p>
*
* It is imperative that the user manually synchronize on the returned
* sorted map when iterating over any of its collection views, or the
* collections views of any of its <tt>subMap</tt>, <tt>headMap</tt> or
* <tt>tailMap</tt> views.
* <pre>
* SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
* ...
* Set s = m.keySet(); // Needn't be in synchronized block
* ...
* synchronized (m) { // Synchronizing on m, not s!
* Iterator i = s.iterator(); // Must be in synchronized block
* while (i.hasNext())
* foo(i.next());
* }
* </pre>
* or:
* <pre>
* SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
* SortedMap m2 = m.subMap(foo, bar);
* ...
* Set s2 = m2.keySet(); // Needn't be in synchronized block
* ...
* synchronized (m) { // Synchronizing on m, not m2 or s2!
* Iterator i = s.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 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 to be "wrapped" in a synchronized sorted map.
* @return a synchronized view of the specified sorted map.
*/
public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) {
return new SynchronizedSortedMap<>(m);
}
/**
* @serial include
*/
static class SynchronizedSortedMap<K,V>
extends SynchronizedMap<K,V>
implements SortedMap<K,V>
{
private static final long serialVersionUID = -8798146769416483793L;
private final SortedMap<K,V> sm;
SynchronizedSortedMap(SortedMap<K,V> m) {
super(m);
sm = m;
}
SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) {
super(m, mutex);
sm = m;
}
public Comparator<? super K> comparator() {
synchronized (mutex) {return sm.comparator();}
}
public SortedMap<K,V> subMap(K fromKey, K toKey) {
synchronized (mutex) {
return new SynchronizedSortedMap<>(
sm.subMap(fromKey, toKey), mutex);
}
}
public SortedMap<K,V> headMap(K toKey) {
synchronized (mutex) {
return new SynchronizedSortedMap<>(sm.headMap(toKey), mutex);
}
}
public SortedMap<K,V> tailMap(K fromKey) {
synchronized (mutex) {
return new SynchronizedSortedMap<>(sm.tailMap(fromKey),mutex);
}
}
public K firstKey() {
synchronized (mutex) {return sm.firstKey();}
}
public K lastKey() {
synchronized (mutex) {return sm.lastKey();}
}
}
/**
* Returns a synchronized (thread-safe) navigable map backed by the
* specified navigable map. In order to guarantee serial access, it is
* critical that <strong>all</strong> access to the backing navigable map is
* accomplished through the returned navigable map (or its views).<p>
*
* It is imperative that the user manually synchronize on the returned
* navigable map when iterating over any of its collection views, or the
* collections views of any of its {@code subMap}, {@code headMap} or
* {@code tailMap} views.
* <pre>
* NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
* ...
* Set s = m.keySet(); // Needn't be in synchronized block
* ...
* synchronized (m) { // Synchronizing on m, not s!
* Iterator i = s.iterator(); // Must be in synchronized block
* while (i.hasNext())
* foo(i.next());
* }
* </pre>
* or:
* <pre>
* NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
* NavigableMap m2 = m.subMap(foo, true, bar, false);
* ...
* Set s2 = m2.keySet(); // Needn't be in synchronized block
* ...
* synchronized (m) { // Synchronizing on m, not m2 or s2!
* Iterator i = s.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 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 to be "wrapped" in a synchronized navigable
* map
* @return a synchronized view of the specified navigable map.
* @since 1.8
*/
public static <K,V> NavigableMap<K,V> synchronizedNavigableMap(NavigableMap<K,V> m) {
return new SynchronizedNavigableMap<>(m);
}
/**
* A synchronized NavigableMap.
*
* @serial include
*/
static class SynchronizedNavigableMap<K,V>
extends SynchronizedSortedMap<K,V>
implements NavigableMap<K,V>
{
private static final long serialVersionUID = 699392247599746807L;
private final NavigableMap<K,V> nm;
SynchronizedNavigableMap(NavigableMap<K,V> m) {
super(m);
nm = m;
}
SynchronizedNavigableMap(NavigableMap<K,V> m, Object mutex) {
super(m, mutex);
nm = m;
}
public Entry<K, V> lowerEntry(K key)
{ synchronized (mutex) { return nm.lowerEntry(key); } }
public K lowerKey(K key)
{ synchronized (mutex) { return nm.lowerKey(key); } }
public Entry<K, V> floorEntry(K key)
{ synchronized (mutex) { return nm.floorEntry(key); } }
public K floorKey(K key)
{ synchronized (mutex) { return nm.floorKey(key); } }
public Entry<K, V> ceilingEntry(K key)
{ synchronized (mutex) { return nm.ceilingEntry(key); } }
public K ceilingKey(K key)
{ synchronized (mutex) { return nm.ceilingKey(key); } }
public Entry<K, V> higherEntry(K key)
{ synchronized (mutex) { return nm.higherEntry(key); } }
public K higherKey(K key)
{ synchronized (mutex) { return nm.higherKey(key); } }
public Entry<K, V> firstEntry()
{ synchronized (mutex) { return nm.firstEntry(); } }
public Entry<K, V> lastEntry()
{ synchronized (mutex) { return nm.lastEntry(); } }
public Entry<K, V> pollFirstEntry()
{ synchronized (mutex) { return nm.pollFirstEntry(); } }
public Entry<K, V> pollLastEntry()
{ synchronized (mutex) { return nm.pollLastEntry(); } }
public NavigableMap<K, V> descendingMap() {
synchronized (mutex) {
return
new SynchronizedNavigableMap<>(nm.descendingMap(), mutex);
}
}
public NavigableSet<K> keySet() {
return navigableKeySet();
}
public NavigableSet<K> navigableKeySet() {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(nm.navigableKeySet(), mutex);
}
}
public NavigableSet<K> descendingKeySet() {
synchronized (mutex) {
return new SynchronizedNavigableSet<>(nm.descendingKeySet(), mutex);
}
}
public SortedMap<K,V> subMap(K fromKey, K toKey) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(
nm.subMap(fromKey, true, toKey, false), mutex);
}
}
public SortedMap<K,V> headMap(K toKey) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(nm.headMap(toKey, false), mutex);
}
}
public SortedMap<K,V> tailMap(K fromKey) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(nm.tailMap(fromKey, true),mutex);
}
}
public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(
nm.subMap(fromKey, fromInclusive, toKey, toInclusive), mutex);
}
}
public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(
nm.headMap(toKey, inclusive), mutex);
}
}
public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
synchronized (mutex) {
return new SynchronizedNavigableMap<>(
nm.tailMap(fromKey, inclusive), mutex);
}
}
}
// Dynamically typesafe collection wrappers
/**
* Returns a dynamically typesafe view of the specified collection.
* Any attempt to insert an element of the wrong type will result in an
* immediate {@link ClassCastException}. Assuming a collection
* contains no incorrectly typed elements prior to the time a
* dynamically typesafe view is generated, and that all subsequent
* access to the collection takes place through the view, it is
* <i>guaranteed</i> that the collection cannot contain an incorrectly
* typed element.
*
* <p>The generics mechanism in the language provides compile-time
* (static) type checking, but it is possible to defeat this mechanism
* with unchecked casts. Usually this is not a problem, as the compiler
* issues warnings on all such unchecked operations. There are, however,
* times when static type checking alone is not sufficient. For example,
* suppose a collection is passed to a third-party library and it is
* imperative that the library code not corrupt the collection by
* inserting an element of the wrong type.
*
* <p>Another use of dynamically typesafe views is debugging. Suppose a
* program fails with a {@code ClassCastException}, indicating that an
* incorrectly typed element was put into a parameterized collection.
* Unfortunately, the exception can occur at any time after the erroneous
* element is inserted, so it typically provides little or no information
* as to the real source of the problem. If the problem is reproducible,
* one can quickly determine its source by temporarily modifying the
* program to wrap the collection with a dynamically typesafe view.
* For example, this declaration:
* <pre> {@code
* Collection<String> c = new HashSet<>();
* }</pre>
* may be replaced temporarily by this one:
* <pre> {@code
* Collection<String> c = Collections.checkedCollection(
* new HashSet<>(), String.class);
* }</pre>
* Running the program again will cause it to fail at the point where
* an incorrectly typed element is inserted into the collection, clearly
* identifying the source of the problem. Once the problem is fixed, the
* modified declaration may be reverted back to the original.
*
* <p>The returned collection does <i>not</i> pass the hashCode and equals
* operations through to the backing collection, but relies on
* {@code Object}'s {@code equals} and {@code 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.
*
* <p>Since {@code null} is considered to be a value of any reference
* type, the returned collection permits insertion of null elements
* whenever the backing collection does.
*
* @param <E> the class of the objects in the collection
* @param c the collection for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code c} is permitted to hold
* @return a dynamically typesafe view of the specified collection
* @since 1.5
*/
public static <E> Collection<E> checkedCollection(Collection<E> c,
Class<E> type) {
return new CheckedCollection<>(c, type);
}
@SuppressWarnings("unchecked")
static <T> T[] zeroLengthArray(Class<T> type) {
return (T[]) Array.newInstance(type, 0);
}
/**
* @serial include
*/
static class CheckedCollection<E> implements Collection<E>, Serializable {
private static final long serialVersionUID = 1578914078182001775L;
final Collection<E> c;
final Class<E> type;
@SuppressWarnings("unchecked")
E typeCheck(Object o) {
if (o != null && !type.isInstance(o))
throw new ClassCastException(badElementMsg(o));
return (E) o;
}
private String badElementMsg(Object o) {
return "Attempt to insert " + o.getClass() +
" element into collection with element type " + type;
}
CheckedCollection(Collection<E> c, Class<E> type) {
this.c = Objects.requireNonNull(c, "c");
this.type = Objects.requireNonNull(type, "type");
}
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 boolean remove(Object o) { return c.remove(o); }
public void clear() { c.clear(); }
public boolean containsAll(Collection<?> coll) {
return c.containsAll(coll);
}
public boolean removeAll(Collection<?> coll) {
return c.removeAll(coll);
}
public boolean retainAll(Collection<?> coll) {
return c.retainAll(coll);
}
public Iterator<E> iterator() {
// JDK-6363904 - unwrapped iterator could be typecast to
// ListIterator with unsafe set()
final Iterator<E> it = c.iterator();
return new Iterator<E>() {
public boolean hasNext() { return it.hasNext(); }
public E next() { return it.next(); }
public void remove() { it.remove(); }};
}
public boolean add(E e) { return c.add(typeCheck(e)); }
private E[] zeroLengthElementArray; // Lazily initialized
private E[] zeroLengthElementArray() {
return zeroLengthElementArray != null ? zeroLengthElementArray :
(zeroLengthElementArray = zeroLengthArray(type));
}
@SuppressWarnings("unchecked")
Collection<E> checkedCopyOf(Collection<? extends E> coll) {
Object[] a;
try {
E[] z = zeroLengthElementArray();
a = coll.toArray(z);
// Defend against coll violating the toArray contract
if (a.getClass() != z.getClass())
a = Arrays.copyOf(a, a.length, z.getClass());
} catch (ArrayStoreException ignore) {
// To get better and consistent diagnostics,
// we call typeCheck explicitly on each element.
// We call clone() to defend against coll retaining a
// reference to the returned array and storing a bad
// element into it after it has been type checked.
a = coll.toArray().clone();
for (Object o : a)
typeCheck(o);
}
// A slight abuse of the type system, but safe here.
return (Collection<E>) Arrays.asList(a);
}
public boolean addAll(Collection<? extends E> coll) {
// Doing things this way insulates us from concurrent changes
// in the contents of coll and provides all-or-nothing
// semantics (which we wouldn't get if we type-checked each
// element as we added it)
return c.addAll(checkedCopyOf(coll));
}
// Override default methods in Collection
@Override
public void forEach(Consumer<? super E> action) {c.forEach(action);}
@Override
public boolean removeIf(Predicate<? super E> filter) {
return c.removeIf(filter);
}
@Override
public Spliterator<E> spliterator() {return c.spliterator();}
@Override
public Stream<E> stream() {return c.stream();}
@Override
public Stream<E> parallelStream() {return c.parallelStream();}
}
/**
* Returns a dynamically typesafe view of the specified queue.
* Any attempt to insert an element of the wrong type will result in
* an immediate {@link ClassCastException}. Assuming a queue contains
* no incorrectly typed elements prior to the time a dynamically typesafe
* view is generated, and that all subsequent access to the queue
* takes place through the view, it is <i>guaranteed</i> that the
* queue cannot contain an incorrectly typed element.
*
* <p>A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link #checkedCollection
* checkedCollection} method.
*
* <p>The returned queue will be serializable if the specified queue
* is serializable.
*
* <p>Since {@code null} is considered to be a value of any reference
* type, the returned queue permits insertion of {@code null} elements
* whenever the backing queue does.
*
* @param <E> the class of the objects in the queue
* @param queue the queue for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code queue} is permitted to hold
* @return a dynamically typesafe view of the specified queue
* @since 1.8
*/
public static <E> Queue<E> checkedQueue(Queue<E> queue, Class<E> type) {
return new CheckedQueue<>(queue, type);
}
/**
* @serial include
*/
static class CheckedQueue<E>
extends CheckedCollection<E>
implements Queue<E>, Serializable
{
private static final long serialVersionUID = 1433151992604707767L;
final Queue<E> queue;
CheckedQueue(Queue<E> queue, Class<E> elementType) {
super(queue, elementType);
this.queue = queue;
}
public E element() {return queue.element();}
public boolean equals(Object o) {return o == this || c.equals(o);}
public int hashCode() {return c.hashCode();}
public E peek() {return queue.peek();}
public E poll() {return queue.poll();}
public E remove() {return queue.remove();}
public boolean offer(E e) {return queue.offer(typeCheck(e));}
}
/**
* Returns a dynamically typesafe view of the specified set.
* Any attempt to insert an element of the wrong type will result in
* an immediate {@link ClassCastException}. Assuming a set contains
* no incorrectly typed elements prior to the time a dynamically typesafe
* view is generated, and that all subsequent access to the set
* takes place through the view, it is <i>guaranteed</i> that the
* set cannot contain an incorrectly typed element.
*
* <p>A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link #checkedCollection
* checkedCollection} method.
*
* <p>The returned set will be serializable if the specified set is
* serializable.
*
* <p>Since {@code null} is considered to be a value of any reference
* type, the returned set permits insertion of null elements whenever
* the backing set does.
*
* @param <E> the class of the objects in the set
* @param s the set for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code s} is permitted to hold
* @return a dynamically typesafe view of the specified set
* @since 1.5
*/
public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) {
return new CheckedSet<>(s, type);
}
/**
* @serial include
*/
static class CheckedSet<E> extends CheckedCollection<E>
implements Set<E>, Serializable
{
private static final long serialVersionUID = 4694047833775013803L;
CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); }
public boolean equals(Object o) { return o == this || c.equals(o); }
public int hashCode() { return c.hashCode(); }
}
/**
* Returns a dynamically typesafe view of the specified sorted set.
* Any attempt to insert an element of the wrong type will result in an
* immediate {@link ClassCastException}. Assuming a sorted set
* contains no incorrectly typed elements prior to the time a
* dynamically typesafe view is generated, and that all subsequent
* access to the sorted set takes place through the view, it is
* <i>guaranteed</i> that the sorted set cannot contain an incorrectly
* typed element.
*
* <p>A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link #checkedCollection
* checkedCollection} method.
*
* <p>The returned sorted set will be serializable if the specified sorted
* set is serializable.
*
* <p>Since {@code null} is considered to be a value of any reference
* type, the returned sorted set permits insertion of null elements
* whenever the backing sorted set does.
*
* @param <E> the class of the objects in the set
* @param s the sorted set for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code s} is permitted to hold
* @return a dynamically typesafe view of the specified sorted set
* @since 1.5
*/
public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s,
Class<E> type) {
return new CheckedSortedSet<>(s, type);
}
/**
* @serial include
*/
static class CheckedSortedSet<E> extends CheckedSet<E>
implements SortedSet<E>, Serializable
{
private static final long serialVersionUID = 1599911165492914959L;
private final SortedSet<E> ss;
CheckedSortedSet(SortedSet<E> s, Class<E> type) {
super(s, type);
ss = s;
}
public Comparator<? super E> comparator() { return ss.comparator(); }
public E first() { return ss.first(); }
public E last() { return ss.last(); }
public SortedSet<E> subSet(E fromElement, E toElement) {
return checkedSortedSet(ss.subSet(fromElement,toElement), type);
}
public SortedSet<E> headSet(E toElement) {
return checkedSortedSet(ss.headSet(toElement), type);
}
public SortedSet<E> tailSet(E fromElement) {
return checkedSortedSet(ss.tailSet(fromElement), type);
}
}
/**
* Returns a dynamically typesafe view of the specified navigable set.
* Any attempt to insert an element of the wrong type will result in an
* immediate {@link ClassCastException}. Assuming a navigable set
* contains no incorrectly typed elements prior to the time a
* dynamically typesafe view is generated, and that all subsequent
* access to the navigable set takes place through the view, it is
* <em>guaranteed</em> that the navigable set cannot contain an incorrectly
* typed element.
*
* <p>A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link #checkedCollection
* checkedCollection} method.
*
* <p>The returned navigable set will be serializable if the specified
* navigable set is serializable.
*
* <p>Since {@code null} is considered to be a value of any reference
* type, the returned navigable set permits insertion of null elements
* whenever the backing sorted set does.
*
* @param <E> the class of the objects in the set
* @param s the navigable set for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code s} is permitted to hold
* @return a dynamically typesafe view of the specified navigable set
* @since 1.8
*/
public static <E> NavigableSet<E> checkedNavigableSet(NavigableSet<E> s,
Class<E> type) {
return new CheckedNavigableSet<>(s, type);
}
/**
* @serial include
*/
static class CheckedNavigableSet<E> extends CheckedSortedSet<E>
implements NavigableSet<E>, Serializable
{
private static final long serialVersionUID = -5429120189805438922L;
private final NavigableSet<E> ns;
CheckedNavigableSet(NavigableSet<E> s, Class<E> type) {
super(s, type);
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() { return ns.pollFirst(); }
public E pollLast() {return ns.pollLast(); }
public NavigableSet<E> descendingSet()
{ return checkedNavigableSet(ns.descendingSet(), type); }
public Iterator<E> descendingIterator()
{return checkedNavigableSet(ns.descendingSet(), type).iterator(); }
public NavigableSet<E> subSet(E fromElement, E toElement) {
return checkedNavigableSet(ns.subSet(fromElement, true, toElement, false), type);
}
public NavigableSet<E> headSet(E toElement) {
return checkedNavigableSet(ns.headSet(toElement, false), type);
}
public NavigableSet<E> tailSet(E fromElement) {
return checkedNavigableSet(ns.tailSet(fromElement, true), type);
}
public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
return checkedNavigableSet(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), type);
}
public NavigableSet<E> headSet(E toElement, boolean inclusive) {
return checkedNavigableSet(ns.headSet(toElement, inclusive), type);
}
public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
return checkedNavigableSet(ns.tailSet(fromElement, inclusive), type);
}
}
/**
* Returns a dynamically typesafe view of the specified list.
* Any attempt to insert an element of the wrong type will result in
* an immediate {@link ClassCastException}. Assuming a list contains
* no incorrectly typed elements prior to the time a dynamically typesafe
* view is generated, and that all subsequent access to the list
* takes place through the view, it is <i>guaranteed</i> that the
* list cannot contain an incorrectly typed element.
*
* <p>A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link #checkedCollection
* checkedCollection} method.
*
* <p>The returned list will be serializable if the specified list
* is serializable.
*
* <p>Since {@code null} is considered to be a value of any reference
* type, the returned list permits insertion of null elements whenever
* the backing list does.
*
* @param <E> the class of the objects in the list
* @param list the list for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code list} is permitted to hold
* @return a dynamically typesafe view of the specified list
* @since 1.5
*/
public static <E> List<E> checkedList(List<E> list, Class<E> type) {
return (list instanceof RandomAccess ?
new CheckedRandomAccessList<>(list, type) :
new CheckedList<>(list, type));
}
/**
* @serial include
*/
static class CheckedList<E>
extends CheckedCollection<E>
implements List<E>
{
private static final long serialVersionUID = 65247728283967356L;
final List<E> list;
CheckedList(List<E> list, Class<E> type) {
super(list, type);
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 remove(int index) { return list.remove(index); }
public int indexOf(Object o) { return list.indexOf(o); }
public int lastIndexOf(Object o) { return list.lastIndexOf(o); }
public E set(int index, E element) {
return list.set(index, typeCheck(element));
}
public void add(int index, E element) {
list.add(index, typeCheck(element));
}
public boolean addAll(int index, Collection<? extends E> c) {
return list.addAll(index, checkedCopyOf(c));
}
public ListIterator<E> listIterator() { return listIterator(0); }
public ListIterator<E> listIterator(final int index) {
final ListIterator<E> i = list.listIterator(index);
return new ListIterator<E>() {
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() { i.remove(); }
public void set(E e) {
i.set(typeCheck(e));
}
public void add(E e) {
i.add(typeCheck(e));
}
@Override
public void forEachRemaining(Consumer<? super E> action) {
i.forEachRemaining(action);
}
};
}
public List<E> subList(int fromIndex, int toIndex) {
return new CheckedList<>(list.subList(fromIndex, toIndex), type);
}
/**
* {@inheritDoc}
*
* @throws ClassCastException if the class of an element returned by the
* operator prevents it from being added to this collection. The
* exception may be thrown after some elements of the list have
* already been replaced.
*/
@Override
public void replaceAll(UnaryOperator<E> operator) {
Objects.requireNonNull(operator);
list.replaceAll(e -> typeCheck(operator.apply(e)));
}
@Override
public void sort(Comparator<? super E> c) {
list.sort(c);
}
}
/**
* @serial include
*/
static class CheckedRandomAccessList<E> extends CheckedList<E>
implements RandomAccess
{
private static final long serialVersionUID = 1638200125423088369L;
CheckedRandomAccessList(List<E> list, Class<E> type) {
super(list, type);
}
public List<E> subList(int fromIndex, int toIndex) {
return new CheckedRandomAccessList<>(
list.subList(fromIndex, toIndex), type);
}
}
/**
* Returns a dynamically typesafe view of the specified map.
* Any attempt to insert a mapping whose key or value have the wrong
* type will result in an immediate {@link ClassCastException}.
* Similarly, any attempt to modify the value currently associated with
* a key will result in an immediate {@link ClassCastException},
* whether the modification is attempted directly through the map
* itself, or through a {@link Map.Entry} instance obtained from the
* map's {@link Map#entrySet() entry set} view.
*
* <p>Assuming a map contains no incorrectly typed keys or values
* prior to the time a dynamically typesafe view is generated, and
* that all subsequent access to the map takes place through the view
* (or one of its collection views), it is <i>guaranteed</i> that the
* map cannot contain an incorrectly typed key or value.
*
* <p>A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link #checkedCollection
* checkedCollection} method.
*
* <p>The returned map will be serializable if the specified map is
* serializable.
*
* <p>Since {@code null} is considered to be a value of any reference
* type, the returned map permits insertion of null keys or values
* whenever the backing map does.
*
* @param <K> the class of the map keys
* @param <V> the class of the map values
* @param m the map for which a dynamically typesafe view is to be
* returned
* @param keyType the type of key that {@code m} is permitted to hold
* @param valueType the type of value that {@code m} is permitted to hold
* @return a dynamically typesafe view of the specified map
* @since 1.5
*/
public static <K, V> Map<K, V> checkedMap(Map<K, V> m,
Class<K> keyType,
Class<V> valueType) {
return new CheckedMap<>(m, keyType, valueType);
}
/**
* @serial include
*/
private static class CheckedMap<K,V>
implements Map<K,V>, Serializable
{
private static final long serialVersionUID = 5742860141034234728L;
private final Map<K, V> m;
final Class<K> keyType;
final Class<V> valueType;
private void typeCheck(Object key, Object value) {
if (key != null && !keyType.isInstance(key))
throw new ClassCastException(badKeyMsg(key));
if (value != null && !valueType.isInstance(value))
throw new ClassCastException(badValueMsg(value));
}
private BiFunction<? super K, ? super V, ? extends V> typeCheck(
BiFunction<? super K, ? super V, ? extends V> func) {
Objects.requireNonNull(func);
return (k, v) -> {
V newValue = func.apply(k, v);
typeCheck(k, newValue);
return newValue;
};
}
private String badKeyMsg(Object key) {
return "Attempt to insert " + key.getClass() +
" key into map with key type " + keyType;
}
private String badValueMsg(Object value) {
return "Attempt to insert " + value.getClass() +
" value into map with value type " + valueType;
}
CheckedMap(Map<K, V> m, Class<K> keyType, Class<V> valueType) {
this.m = Objects.requireNonNull(m);
this.keyType = Objects.requireNonNull(keyType);
this.valueType = Objects.requireNonNull(valueType);
}
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 v) { return m.containsValue(v); }
public V get(Object key) { return m.get(key); }
public V remove(Object key) { return m.remove(key); }
public void clear() { m.clear(); }
public Set<K> keySet() { return m.keySet(); }
public Collection<V> values() { return m.values(); }
public boolean equals(Object o) { return o == this || m.equals(o); }
public int hashCode() { return m.hashCode(); }
public String toString() { return m.toString(); }
public V put(K key, V value) {
typeCheck(key, value);
return m.put(key, value);
}
@SuppressWarnings("unchecked")
public void putAll(Map<? extends K, ? extends V> t) {
// Satisfy the following goals:
// - good diagnostics in case of type mismatch
// - all-or-nothing semantics
// - protection from malicious t
// - correct behavior if t is a concurrent map
Object[] entries = t.entrySet().toArray();
List<Map.Entry<K,V>> checked = new ArrayList<>(entries.length);
for (Object o : entries) {
Map.Entry<?,?> e = (Map.Entry<?,?>) o;
Object k = e.getKey();
Object v = e.getValue();
typeCheck(k, v);
checked.add(
new AbstractMap.SimpleImmutableEntry<>((K)k, (V)v));
}
for (Map.Entry<K,V> e : checked)
m.put(e.getKey(), e.getValue());
}
private transient Set<Map.Entry<K,V>> entrySet;
public Set<Map.Entry<K,V>> entrySet() {
if (entrySet==null)
entrySet = new CheckedEntrySet<>(m.entrySet(), valueType);
return entrySet;
}
// Override default methods in Map
@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) {
m.replaceAll(typeCheck(function));
}
@Override
public V putIfAbsent(K key, V value) {
typeCheck(key, value);
return m.putIfAbsent(key, value);
}
@Override
public boolean remove(Object key, Object value) {
return m.remove(key, value);
}
@Override
public boolean replace(K key, V oldValue, V newValue) {
typeCheck(key, newValue);
return m.replace(key, oldValue, newValue);
}
@Override
public V replace(K key, V value) {
typeCheck(key, value);
return m.replace(key, value);
}
@Override
public V computeIfAbsent(K key,
Function<? super K, ? extends V> mappingFunction) {
Objects.requireNonNull(mappingFunction);
return m.computeIfAbsent(key, k -> {
V value = mappingFunction.apply(k);
typeCheck(k, value);
return value;
});
}
@Override
public V computeIfPresent(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
return m.computeIfPresent(key, typeCheck(remappingFunction));
}
@Override
public V compute(K key,
BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
return m.compute(key, typeCheck(remappingFunction));
}
@Override
public V merge(K key, V value,
BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
Objects.requireNonNull(remappingFunction);
return m.merge(key, value, (v1, v2) -> {
V newValue = remappingFunction.apply(v1, v2);
typeCheck(null, newValue);
return newValue;
});
}
/**
* We need this class in addition to CheckedSet as Map.Entry permits
* modification of the backing Map via the setValue operation. This
* class is subtle: there are many possible attacks that must be
* thwarted.
*
* @serial exclude
*/
static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> {
private final Set<Map.Entry<K,V>> s;
private final Class<V> valueType;
CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) {
this.s = s;
this.valueType = valueType;
}
public int size() { return s.size(); }
public boolean isEmpty() { return s.isEmpty(); }
public String toString() { return s.toString(); }
public int hashCode() { return s.hashCode(); }
public void clear() { s.clear(); }
public boolean add(Map.Entry<K, V> e) {
throw new UnsupportedOperationException();
}
public boolean addAll(Collection<? extends Map.Entry<K, V>> coll) {
throw new UnsupportedOperationException();
}
public Iterator<Map.Entry<K,V>> iterator() {
final Iterator<Map.Entry<K, V>> i = s.iterator();
final Class<V> valueType = this.valueType;
return new Iterator<Map.Entry<K,V>>() {
public boolean hasNext() { return i.hasNext(); }
public void remove() { i.remove(); }
public Map.Entry<K,V> next() {
return checkedEntry(i.next(), valueType);
}
};
}
@SuppressWarnings("unchecked")
public Object[] toArray() {
Object[] source = s.toArray();
/*
* Ensure that we don't get an ArrayStoreException even if
* s.toArray returns an array of something other than Object
*/
Object[] dest = (CheckedEntry.class.isInstance(
source.getClass().getComponentType()) ? source :
new Object[source.length]);
for (int i = 0; i < source.length; i++)
dest[i] = checkedEntry((Map.Entry<K,V>)source[i],
valueType);
return dest;
}
@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) {
// We don't pass a to s.toArray, to avoid window of
// vulnerability wherein an unscrupulous multithreaded client
// could get his hands on raw (unwrapped) Entries from s.
T[] arr = s.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
for (int i=0; i<arr.length; i++)
arr[i] = (T) checkedEntry((Map.Entry<K,V>)arr[i],
valueType);
if (arr.length > a.length)
return 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;
Map.Entry<?,?> e = (Map.Entry<?,?>) o;
return s.contains(
(e instanceof CheckedEntry) ? e : checkedEntry(e, valueType));
}
/**
* The bulk collection methods are overridden to protect
* against an unscrupulous collection whose contains(Object o)
* method senses when o is a Map.Entry, and calls o.setValue.
*/
public boolean containsAll(Collection<?> c) {
for (Object o : c)
if (!contains(o)) // Invokes safe contains() above
return false;
return true;
}
public boolean remove(Object o) {
if (!(o instanceof Map.Entry))
return false;
return s.remove(new AbstractMap.SimpleImmutableEntry
<>((Map.Entry<?,?>)o));
}
public boolean removeAll(Collection<?> c) {
return batchRemove(c, false);
}
public boolean retainAll(Collection<?> c) {
return batchRemove(c, true);
}
private boolean batchRemove(Collection<?> c, boolean complement) {
Objects.requireNonNull(c);
boolean modified = false;
Iterator<Map.Entry<K,V>> it = iterator();
while (it.hasNext()) {
if (c.contains(it.next()) != complement) {
it.remove();
modified = true;
}
}
return modified;
}
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof Set))
return false;
Set<?> that = (Set<?>) o;
return that.size() == s.size()
&& containsAll(that); // Invokes safe containsAll() above
}
static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e,
Class<T> valueType) {
return new CheckedEntry<>(e, valueType);
}
/**
* 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 CheckedEntry<K,V,T> implements Map.Entry<K,V> {
private final Map.Entry<K, V> e;
private final Class<T> valueType;
CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) {
this.e = Objects.requireNonNull(e);
this.valueType = Objects.requireNonNull(valueType);
}
public K getKey() { return e.getKey(); }
public V getValue() { return e.getValue(); }
public int hashCode() { return e.hashCode(); }
public String toString() { return e.toString(); }
public V setValue(V value) {
if (value != null && !valueType.isInstance(value))
throw new ClassCastException(badValueMsg(value));
return e.setValue(value);
}
private String badValueMsg(Object value) {
return "Attempt to insert " + value.getClass() +
" value into map with value type " + valueType;
}
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof Map.Entry))
return false;
return e.equals(new AbstractMap.SimpleImmutableEntry
<>((Map.Entry<?,?>)o));
}
}
}
}
JDK 工具类之 Collections 2
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