Java 多线程与高并发，高级java面试题及答案整理_高并发面试题java

private Singleton(String name) {

this.name = name;

}

public static Singleton getInstance() {

if (null == INSTANCE) {

synchronized (Singleton.class) {

if (null == INSTANCE) {

// 可能会出现指令重排序，即未进行成员变量name的初始化就退出了，

// 这样别人就会拿到未初始化(name=null)的Singleton对象

INSTANCE = new Singleton(“hh”);

}

}

}

return INSTANCE;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

}

• 不保证原子性

package com.nobody.thread;

import java.util.ArrayList;

import java.util.List;

/**

• volatile不保证原子性，最终结果一般小于10000

• 若要保证原子性，直接将doCount方法加synchronized关键字即可，而volatile可有可无

• @author Μr.ηobοdy

• @date 2020-04-19

*/

public class VolatileDemo1 {

private volatile static int count = 0;

private /synchronized/ void doCount() {

for (int i = 0; i < 1000; i++) {

count++;

}

}

public static void main(String[] args) {

VolatileDemo1 v = new VolatileDemo1();

// 启动10个线程

List threads = new ArrayList<>();

for (int i = 1; i <= 10; i++) {

threads.add(new Thread(v::doCount, “