设计模式之懒汉单例非线程安全

package design.singletonLazy.demo;

public class Main {

    public static void main(String[] args) {
        // 创建多线程验证
        Thread t1 = new Thread() {
            @Override
            public void run() {
                SingletonLazyUnsafetyEntity s = SingletonLazyUnsafetyEntity.getSingletonEntity();
                System.out.println("t1线程获取对象的hashcode: " + s.hashCode());
            }
        };
        Thread t2 = new Thread() {
            @Override
            public void run() {
                SingletonLazyUnsafetyEntity s = SingletonLazyUnsafetyEntity.getSingletonEntity();
                System.out.println("t2线程获取对象的hashcode: " + s.hashCode());
            }
        };
        Thread t3 = new Thread() {
            @Override
            public void run() {
                SingletonLazyUnsafetyEntity s = SingletonLazyUnsafetyEntity.getSingletonEntity();
                System.out.println("t3线程获取对象的hashcode: " + s.hashCode());
            }
        };
        t1.start();
        t2.start();
        t3.start();
    }

}
//如果相同则多启动几次试试
// t1线程获取对象的hashcode: 475341210
// t2线程获取对象的hashcode: 162086129
// t3线程获取对象的hashcode: 162086129

package design.singletonLazy.demo;

//懒汉式单例-非线程安全
public class SingletonLazyUnsafetyEntity {

    // 直接创建对象实例
    private static SingletonLazyUnsafetyEntity s = null;

    // 实例输出出口
    public static SingletonLazyUnsafetyEntity getSingletonEntity() {
        if (s == null) {
            s = new SingletonLazyUnsafetyEntity();
        }
        return s;
    }

    // 私有化构造方法,让外部无法通过new创建
    private SingletonLazyUnsafetyEntity() {

    }
}