Java 设计模式 单例模式 Singleton
1.懒汉（线程安全）
//懒汉
public class Singleton {
private static Singleton singleton;
private Singleton() {
}
public static synchronized Singleton getSingleton() {
if (singleton == null) {
singleton = new Singleton();
}
return singleton;
}
}
2.饿汉
//饿汉
public class Singleton {
private static final Singleton singleton = new Singleton();
private Singleton () {
}
public static Singleton getSingleton() {
return singleton;
}
}
3.静态内部类
//静态内部类
public class Singleton {
private static class SingletonHolder {
private static final Singleton singleton = new Singleton();
}
private Singleton() {
}
public static Singleton getSingleton() {
return SingletonHolder.singleton;
}
}
4.枚举
//枚举
public enum Singleton {
INSTANCE;
public void whateverMethod() {
}
}
5.double-lock
//double-lock
public class Singleton {
private volatile static Singleton singleton;
private Singleton() {
}
public static Singleton getSingleton() {
if (singleton == null) {
synchronized(Singleton.class) {
if (singleton == null) {
singleton = new Singleton();
}
}
}
return singleton;
}
}
