Five ways to implement singleton patterns in Java

[code] Five ways to implement singleton patterns in Java

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package singleton; /** * @author lei * 单例模式的五种写法： * 1、懒汉 * 2、恶汉 * 3、静态内部类 * 4、枚举 * 5、双重校验锁 * 2011-9-6 *//** *五、 双重校验锁，在当前的内存模型中无效 */class LockSingleton{    private volatile static LockSingleton singleton;    private LockSingleton(){}         //详见：http://www.ibm.com/developerworks/cn/java/j-dcl.html    public static LockSingleton getInstance(){        if(singleton==null){            synchronized(LockSingleton.class){                if(singleton==null){                    singleton=new LockSingleton();                }            }        }        return singleton;    }     }/** * 四、枚举，《Effective Java》作者推荐使用的方法，优点：不仅能避免多线程同步问题，而且还能防止反序列化重新创建新的对象 */enum EnumSingleton{    INSTANCE;    public void doSomeThing(){    }}/** * 三、静态内部类 优点：加载时不会初始化静态变量INSTANCE，因为没有主动使用，达到Lazy loading */class InternalSingleton{    private static class SingletonHolder{        private final static  InternalSingleton INSTANCE=new InternalSingleton();    }       private InternalSingleton(){}    public static InternalSingleton getInstance(){        return SingletonHolder.INSTANCE;    }}/** * 二、恶汉,缺点：没有达到lazy loading的效果 */class HungrySingleton{    private static HungrySingleton singleton=new HungrySingleton();    private HungrySingleton(){}    public static HungrySingleton getInstance(){        return singleton;    }}/** * 一、懒汉，常用的写法 */class LazySingleton{    private static LazySingleton singleton;    private LazySingleton(){    }    public static LazySingleton getInstance(){        if(singleton==null){            singleton=new LazySingleton();        }        return singleton;    }   }

Five ways to implement singleton patterns in Java