How to write a thread-safe Singleton?

mydaypower1

于 2010-06-03 10:32:00 发布

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CC 4.0 BY-SA版权

文章标签： null class object

本文链接：https://blog.youkuaiyun.com/mydaypower1/article/details/5644116

本文介绍了三种不同的单例模式实现方法：饿汉式、懒汉式同步和双重检查锁定。这些方法确保了类的实例唯一，并提供了全局访问点。

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[Method 1]





public

 class

 MySingleton 

{


    private

 static

 MySingleton instance = new

 MySingleton();

    private

 MySingleton() 

    {


        // construct the singleton instance


    }


    

    public

 static

 MySingleton getInstance() 

    {


        return

 instance;

    }


}





[Method 2]




public

 class

 MySingleton {


    private

 static

 MySingleton instance = null

;

    private

 MySingleton() {


        // construct the singleton instance


    }


    public

 synchronized static

 MySingleton getInstance() {


        if

 (instance == null

) {


            instance = new

 MySingleton();

        }


        return

 instance;

    }


}





[Method 3]




public

 class

 MySingleton {


    private

 static

 boolean

 initialized = false

;

    private

 static

 Object lock = new

 Object();

    private

 static

 MySingleton instance = null

;

    private

 MySingleton() {


        // construct the singleton instance


    }


    public

 static

 MySingleton getInstance() {


        if

 (!initialized) {


            synchronized

(lock) {


                if

 (instance == null

) {


                    instance = new

 MySingleton();

                    initialized = true

;

                }


            }


        }


        return

 instance;

    }


}