线程安全的单例模式

直接上代码

ublic class Singleton {
    public Singleton() {
        super();
        System.out.println("single");
    }

    private static class Inner{
        private static Singleton s=new Singleton();
    }

    private static Singleton getSingle(){
        return Inner.s;
    }

    public static void main(String[] args) {
        Thread[] ths=new Thread[200];
        for (int i = 0; i < ths.length; i++) {
            ths[i]=new Thread(()->{
               Singleton.getSingle();
            });
        }
    }
}

public class Singleton {
    private static Singleton sin=new Singleton();    ///直接初始化一个实例对象
    private Singleton(){    ///private类型的构造函数，保证其他类对象不能直接new一个该对象的实例
    }
    public static Singleton getSin(){    ///该类唯一的一个public方法    
        return sin;
    }
}

public class Singleton {  
     private static Singleton instance;  
     private Singleton (){
         
     }   
     public static synchronized Singleton getInstance(){    //对获取实例的方法进行同步
       if (instance == null)     
         instance = new Singleton(); 
       return instance;
     }
 }

public class Singleton {  
     private static Singleton instance;  
     private Singleton (){
     }   
     public static Singleton getInstance(){    //对获取实例的方法进行同步
       if (instance == null){
           synchronized(Singleton.class){
               if (instance == null)
                   instance = new Singleton(); 
           }
       }
       return instance;
     }
     
 }

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