Java设计模式-单例模式-懒汉式（线程不安全）

public class SingletonTest02 {
    public static void main(String[] args) {
        Singleton02 instance  = Singleton02.getInstance();
        Singleton02 instance01 = Singleton02.getInstance();

        System.out.println(instance == instance01);
        System.out.println("instance,hashCode = " + instance.hashCode());
        System.out.println("instance01,hashCode = " + instance01.hashCode());

    }
}

class Singleton02{
    private static Singleton02 singleton;
    private Singleton02(){}
    public static Singleton02 getInstance(){
        if(singleton == null){
            singleton = new Singleton02();
        }
        return singleton;
    }
}

// 运行结果
true
instance,hashCode = 1846274136
instance01,hashCode = 1846274136