单例模式

单例模式

构造器私有

​ 饿汉式

package com.singleMode;

public class Hungry {
private byte[] bytes1 = new byte[1024*1024];
private byte[] bytes2 = new byte[1024*1024];
private byte[] bytes3 = new byte[1024*1024];
private byte[] bytes4 = new byte[1024*1024];
private byte[] bytes5 = new byte[1024*1024];

    private Hungry(){

    }

    private static final Hungry HUNGRY = new Hungry();

    public static Hungry getInstance(){
        return HUNGRY;
    }
}

DLC懒汉式

package com.singleMode;

public class LazyMan {
    private LazyMan(){

    }

    private volatile static LazyMan lazyMan;    //禁止指令重排

    public LazyMan getInstance(){
        if (lazyMan==null){     //双重检测锁模式
            synchronized (LazyMan.class){
                if (lazyMan==null){
                    LazyMan lazyMan = new LazyMan();	//不是原子性操作
                }
            }
        }


        return lazyMan;
    }
}

​ declareConstructor.setAccessible(ture) //反射破坏单例,无视私有化