java multithreaded - Singleton

Singleton
only one external objects, no matter internally, such as every computer has only one task manager
1 is constructed to privatize
2, the interior offers private static properties - the address of the storage object
3, to provide public static methods visit - get properties

public class my {

//2、提供私有静态属性
private volatile static my instance;  //避免new对象时指令重排
//1、构造器私有化
private my(){

}
//3、提供公共静态方法访问属性
public static my getInstance()
{
    if(null!=instance)  //如果已经创建好对象，则不需要多个线程等待创建对象
    {
        return instance;
    }
    synchronized(my.class) //绑定类的模子
    {
    if(null==instance) //多线程可能创建多个对象，加入同步
    {
        instance=new my();//可能发生指令重排
        //new对象发生:1、开辟空间2、初始化对象信息3、返回对象的地址给引用instance
        //过程很慢，可能第三步会提前于第二步，a线程可能在初始化信息的时候 ，b线程可能已经拿到对象
        //加入voliatle避免这种情况
    }
    }
    return instance;

}

public static void main(String[]args) throws InterruptedException
{
//打印对象地址，检验单例模式是否成功
    Thread t=new Thread(()->{
        System.out.println(my.getInstance());
    });
    t.start();
    System.out.println(my.getInstance());
}

}