死锁定义：多个线程互相拥抱着对方需要的资源，然后形成僵持产生死锁的四个必要条件：1、互斥：一个资源每次只能被一个进程使用2、请求与保持：一个进程因请求资源而阻塞时，对已获得的资源保持不放3、不剥夺条件：进程已获得的资源，在未使用完之前，不能强行剥夺4、循环等待：若干进程之间形成一种头尾相接的循环等待资源关系死锁实例：package com.thread.threadDemo; /** * @Author suaxi * @Date 2020/11/26 16:18 * 死锁：多个线程互相拥抱着对方需要的资源，然后形成僵持 */ public class DeadLock { public static void main(String[] args) { MakeUp p1 = new MakeUp(0, "孙笑川"); MakeUp p2 = new MakeUp(1, "药水哥"); p1.start(); p2.start(); } } //口红 class Lipstick{ } //镜子 class Mirror{ } class MakeUp extends Thread{ //需要的资源只有一份，用statick来保证只有一份 static Lipstick lipstick = new Lipstick(); static Mirror mirror = new Mirror(); int choice; //选择 String name; //使用人 public MakeUp(int choice,String name){ this.choice = choice; this.name = name; } @Override public void run() { //化妆 try { makeup(); } catch (InterruptedException e) { e.printStackTrace(); } } private void makeup() throws InterruptedException { if (choice==0){ synchronized (lipstick){ //拿到口红 System.out.println(this.name+"获得口红的锁"); Thread.sleep(1000); synchronized (mirror){ //等待一秒后想拿镜子 System.out.println(this.name+"获得镜子的锁"); } } }else { synchronized (mirror){//拿到镜子 System.out.println(this.name+"获得镜子的锁"); Thread.sleep(2000); synchronized (lipstick) { //等待两秒后想拿口红 System.out.println(this.name + "获得口红的锁"); } } } } }将choice==0中的synchronized (mirror)拿到synchronized (lipStick)之外，else中的代码同理，即可解决实例中的死锁问题package com.thread.threadDemo; /** * @Author suaxi * @Date 2020/11/26 16:18 * 死锁：多个线程互相拥抱着对方需要的资源，然后形成僵持 */ public class DeadLock { public static void main(String[] args) { MakeUp p1 = new MakeUp(0, "孙笑川"); MakeUp p2 = new MakeUp(1, "药水哥"); p1.start(); p2.start(); } } //口红 class Lipstick{ } //镜子 class Mirror{ } class MakeUp extends Thread{ //需要的资源只有一份，用statick来保证只有一份 static Lipstick lipstick = new Lipstick(); static Mirror mirror = new Mirror(); int choice; //选择 String name; //使用人 public MakeUp(int choice,String name){ this.choice = choice; this.name = name; } @Override public void run() { //化妆 try { makeup(); } catch (InterruptedException e) { e.printStackTrace(); } } private void makeup() throws InterruptedException { if (choice==0){ synchronized (lipstick){ //拿到口红 System.out.println(this.name+"获得口红的锁"); Thread.sleep(1000); } synchronized (mirror){ //等待一秒后想拿镜子 System.out.println(this.name+"获得镜子的锁"); } }else { synchronized (mirror){//拿到镜子 System.out.println(this.name+"获得镜子的锁"); Thread.sleep(2000); } synchronized (lipstick) { //等待两秒后想拿口红 System.out.println(this.name + "获得口红的锁"); } } } }