线程安全的单例模式

来源：互联网发布：java reactor设计模式编辑：程序博客网时间：2024/06/07 13:56

不使用锁而定义时直接初始化

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

使用synchronized修饰方法

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

双重检查锁定（Double Check Locking)，使用synchronized锁定单例类

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

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