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单例模式实现

日期：2018-07-31点击：509收藏

1. 单线程可用

public class Singleton { private static Singleton singleton; private Singleton() { } public static Singleton getInstance() { if (null == singleton) { singleton = new Singleton(); } return singleton; } }

2. 使用final常量

public class Singleton { private static final Singleton singleton = new Singleton(); private Singleton() { } public static Singleton getInstance() { return singleton; } }

3. 加锁构造

public class Singleton { private static Singleton singleton; private static final Lock LOCK = new ReentrantLock(); private Singleton() { } public static Singleton getInstance() { if (null == singleton) { LOCK.lock(); if (null == singleton) { singleton = new Singleton(); } LOCK.unlock(); } return singleton; } }

4. 方法级加锁

public class Singleton { private static Singleton singleton; private Singleton() { } public static Singleton getInstance() { if (null == singleton) { init(); } return singleton; } private static synchronized void init(){ if(null == singleton){ singleton = new Singleton(); } } }

5. 静态内部类实现，多线程可用

public class Singleton { private Singleton() { } public static Singleton getInstance() { return Container.singleton; } private static class Container { private static Singleton singleton = new Singleton(); } }

6. 拒绝强行反射创建我

public class Singleton { private Singleton() { if (null != Container.singleton) { throw new UnsupportedOperationException(); // 报错啦 } } public static Singleton getInstance() { return Container.singleton; } private static class Container { private static Singleton singleton = new Singleton(); } }

原文链接：https://yq.aliyun.com/articles/621029

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