单例模式，双重校验的懒汉式

Posted 2022-12-22 liyao0312

/**
 * 单例模式，双重校验的懒汉式
 */
public class bTestSingleton 
    public static void main(String[] args) 
        Singleton s1 = Singleton.getInstance();
        Singleton s2 = Singleton.getInstance();
        System.out.println(s1==s2);
    



class Singleton
    private  Singleton()

    

    private static Singleton instance = null;

    public static Singleton getInstance()
        if(instance==null)    //为了不让其他的做无谓的等待，不是空的话直接返回
            synchronized (Singleton.class)   //线程安全
                if (instance == null)        //是空的时候 创建
                    instance = new Singleton();
                
            
        
        return instance;