Java中线程安全的单例模式

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第三种：用“双重检查加锁”，在getInstance中减少使用同步

public class Singleton {

    private volatile static Singleton uniqueInstance = null;

    public static void main(String[] args){
        Singleton singleton = Singleton.getInstance();
    }

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


}