Java-多线程
多线程
- 线程就是独立的执行路径
- 在程序运行时，即使没有自己创建的线程，后台也会有多个线程，如主线程，gc线程
- main（）称之为主线程，为系统的入口，用于执行整个程序
- 在一个进程中，如果开辟了多个线程，线程的运行用调度器安排调度，调度器是与操作系统紧密相关的，先后顺序是不能人为的干预的
- 对同一份资源操作时，会存在资源抢夺的问题，需要加入并发控制
- 线程会带来额外的开销，如CPU调度时间，并发控制开销。
- 每个线程在自己的工作内存交互，内存控制不当会造成数据不一致。
线程创建
Thread类
package com.xiaobai.thread.lesson01;
//创建线程方式一：集成thread类，重写run方法，调用star开启线程
public class TestThread1 extends Thread{
@Override
public void run() {
//run方法线程体
for (int i = 0; i < 20; i++) {
System.out.println("我在看代码-----"+i);
}
}
public static void main(String[] args) {
//创建一个线程对象
TestThread1 testThread1 = new TestThread1();
//调用star方法开启线程
testThread1.start();
for (int i = 0; i < 20; i++) {
System.out.println("我在学习多线程--" + i);
}
}
}
注：线程开启不一定立即执行，由CPU调度
导入jar包
-
下载工具类commons-io
-
导入到项目lib中
-
右键lib文件夹，Add as Library
案例
多线程下载图片
package com.xiaobai.thread.lesson01;
import org.apache.commons.io.FileUtils;
import java.io.File;
import java.io.IOException;
import java.net.URL;
//练习Thread，实现多线程同步下载图片
public class TestThread2 extends Thread {
private String url;
private String name;
public TestThread2(String url, String name) {
this.url = url;
this.name = name;
}
//下载线程的执行体
@Override
public void run() {
WebDownloder webDownloder = new WebDownloder();
webDownloder.downloader(url,name);
System.out.println("下载了文件："+name);
}
public static void main(String[] args) {
TestThread2 t1 = new TestThread2("https://www.baidu.com/img/flexible/logo/plus_logo_web_2.png","百度LOGO");
TestThread2 t2 = new TestThread2("https://mat1.gtimg.com/www/mobi/2017/image/logo-text-whitetext_v2.svg","腾讯LOG");
TestThread2 t3 = new TestThread2("https://yt-adp.ws.126.net/linxue/860125_ajta_20210401.jpg","网易广告");
t1.start();
t2.start();
t3.start();
}
}
//下载器
class WebDownloder {
public void downloader(String url, String name) {
try {
FileUtils.copyURLToFile(new URL(url), new File(name));
} catch (IOException e) {
e.printStackTrace();
System.out.println("IO异常，downloader方法出现问题");
}
}
}
Runnable类
package com.xiaobai.thread.lesson01;
//创建线程方式2，实现runnable方法，重新run方法，执行线程需要丢入runnable接口实现类，调用start方法
public class TestThread3 implements Runnable{
@Override
public void run() {
//run方法线程体
for (int i = 0; i < 20; i++) {
System.out.println("我在看代码-----"+i);
}
}
public static void main(String[] args) {
//创建runnable接口实现类
TestThread3 testThread3 = new TestThread3();
//创建线程对象，通过线程对象来开启我们的线程，代理
Thread thread = new Thread(testThread3);
thread.start();
for (int i = 0; i < 20; i++) {
System.out.println("我在学习多线程--" + i);
}
}
}
package com.xiaobai.thread.lesson01;
//多个线程同时操作同一个对象
//买火车票的例子
public class TestThread4 implements Runnable{
private int tickeNums = 10;
@Override
public void run() {
while (true){
if (tickeNums<=0){
break;
}
try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+"---》拿到了第"+tickeNums--+"票");
}
}
public static void main(String[] args) {
TestThread4 ticket = new TestThread4();
new Thread(ticket,"小明").start();
new Thread(ticket,"老师").start();
new Thread(ticket,"李三").start();
}
}
案例：龟兔赛跑
- 首先来个赛道距离，然后要离终点越来越近
- 判断比赛是否结束
- 打印出胜利者
- 龟兔赛跑开始
- 故事中乌龟是赢的，兔子需要睡觉，所以我们来模拟兔子树胶
package com.xiaobai.thread.lesson01;
public class Race implements Runnable{
private static String winner;
@Override
public void run() {
for (int i = 1; i <= 100; i++) {
if (Thread.currentThread().getName().equals("兔子")&& i%10==0){
try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//判断比赛是否结束
boolean flag = gameOver(i);
if (flag==true){
break;
}
System.out.println(Thread.currentThread().getName()+"--->"+i+"步");
}
}
//判断是否完成比赛
private boolean gameOver(int steps){
//判断是否有胜利者
if (winner!=null){
return true;
}{
if (steps>=100){
winner = Thread.currentThread().getName();
System.out.println("winner is"+winner);
return true;
}
}
return false;
}
public static void main(String[] args) {
Race race = new Race();
new Thread(race,"兔子").start();
new Thread(race,"乌龟").start();
}
}
Callable接口
-
实现Callable接口，需要返回值类型
-
重写call方法，需要抛出异常
-
创建目标对象
-
创建执行服务：
ExecutorService ser = Executors.newFixedThreadPool(1); -
提交执行：
Future<Boolean>result1=ser.submit(t1); -
获取结果：
boolean r1 = result1.get() -
关闭服务：
ser.shutdownNow();
下载案例：
package com.xiaobai.thread.lesson02;
import com.xiaobai.thread.lesson02.WebDownloder;
import org.apache.commons.io.FileUtils;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.*;
public class TestCallable implements Callable<Boolean> {
private String url;
private String name;
public TestCallable(String url, String name) {
this.url = url;
this.name = name;
}
//下载线程的执行体
@Override
public Boolean call() {
WebDownloder webDownloder = new WebDownloder();
webDownloder.downloader(url,name);
System.out.println("下载了文件："+name);
return true;
}
public static void main(String[] args) throws Exception{
TestCallable t1 = new TestCallable("https://www.baidu.com/img/flexible/logo/plus_logo_web_2.png","百度LOGO");
TestCallable t2 = new TestCallable("https://mat1.gtimg.com/www/mobi/2017/image/logo-text-whitetext_v2.svg","腾讯LOG");
TestCallable t3 = new TestCallable("https://yt-adp.ws.126.net/linxue/860125_ajta_20210401.jpg","网易广告");
ExecutorService ser = Executors.newFixedThreadPool(3);
Future<Boolean> r1=ser.submit(t1);
Future<Boolean> r2=ser.submit(t2);
Future<Boolean> r3=ser.submit(t3);
boolean rs1 = r1.get();
boolean rs2 = r2.get();
boolean rs3 = r3.get();
ser.shutdownNow();
}
}
class WebDownloder {
public void downloader(String url, String name) {
try {
FileUtils.copyURLToFile(new URL(url), new File(name));
} catch (IOException e) {
e.printStackTrace();
System.out.println("IO异常，downloader方法出现问题");
}
}
}
静态代理
- 真实对象和代理对象都要实现同一个接口
- 代理对象要代理真实角色
- 好处：代理对象可以做很多真实对象不能做的，真实对象只做自己的事情
package com.xiaobai.thread.lesson02;
public class StacticProxy {
public static void main(String[] args) {
WeddingCompany weddingCompany = new WeddingCompany(new You());
weddingCompany.HappyMarry();
}
}
interface Marry{
void HappyMarry();
}
//真实角色
class You implements Marry{
@Override
public void HappyMarry() {
System.out.println("要结婚了");
}
}
//代理角色
class WeddingCompany implements Marry{
private Marry target;
public WeddingCompany(Marry target) {
this.target = target;
}
@Override
public void HappyMarry() {
before();
this.target.HappyMarry();
after();
}
private void after() {
System.out.println("结婚之后");
}
private void before() {
System.out.println("结婚之前");
}
}
Lambda表达式
- λ希腊字母表中排序第十一位的字母，英文名称为Lambda
- 避免匿名内部类定义过多
- 其实质属于函数式编程的概念
函数式接口
函数式接口的定义：
- 任何接口，如果只包含一个抽象方法，那么它就是一个函数式接口
- 对于函数式接口，我们可以通过lambda表达式来创建该接口对象
lambda表达式推导
lambda推导：
package com.xiaobai.thread.lambda;
/*
推导lambda表达式
*/
public class TestLambda1 {
//3.静态内部类
static class Like2 implements ILike{
@Override
public void lambda() {
System.out.println("I like lambda2");
}
}
public static void main(String[] args) {
ILike like = new Like();
like.lambda();
like = new Like2();
like.lambda();
//4.局部内部类
class Like3 implements ILike {
@Override
public void lambda() {
System.out.println("I like lambda3");
}
}
like = new Like3();
like.lambda();
//5.匿名内部类:没有类的名称，必须借助接口或者父类
like = new ILike() {
@Override
public void lambda() {
System.out.println("I like lambda4");
}
};
like.lambda();
//6.用lambda简化
like = () ->{
System.out.println("I like lambda5");
};
like.lambda();
}
}
//1。定义一个函数式表达式
interface ILike{
void lambda();
}
//2.实现类
class Like implements ILike{
@Override
public void lambda() {
System.out.println("I like lambda");
}
}
lambda表达式简化及注意事项：
注意事项：
- lambda表达式只能有一行代码的情况下才能简化成一行，如果有多行，那么就用代码块包裹
- 前提是接口是函数式接口
- 多个参数也可以去掉参数类型，去掉全部去掉，不去都不去
- 多个参数，必须加括号，如果单个括号可去掉。
package com.xiaobai.thread.lambda;
public class TestLambda2 {
static class Love2 implements ILove{
@Override
public void love(int a) {
System.out.println("I love you--->"+a);
}
}
public static void main(String[] args) {
class Love3 implements ILove{
@Override
public void love(int a) {
System.out.println("I love you--->"+a);
}
}
ILove love = new Love();
love.love(1);
love = new Love2();
love.love(2);
love = new Love3();
love.love(3);
love = new ILove() {
@Override
public void love(int a) {
System.out.println("I love you--->"+a);
}
};
love.love(4);
love = (int a)->{System.out.println("I love you--->"+a);};
love.love(5);
}
}
interface ILove{
void love(int a);
}
class Love implements ILove{
@Override
public void love(int a) {
System.out.println("I love you--->"+a);
}
}
停止线程
- 线程自己停止
- 使用一个标志位进行终止变了，当flag=false,则终止线程
package com.xiaobai.thread.state;
//测试stop
public class TestStop implements Runnable{
//设置一个标志位
private boolean flag = true;
@Override
public void run() {
int i = 0;
while (flag){
System.out.println("run....Thread"+i++);
}
}
//2.设置一个公开的方法停止线程，转换标志位
public void stop(){
this.flag = false;
}
public static void main(String[] args) {
TestStop testStop = new TestStop();
new Thread(testStop).start();
for (int i = 0; i < 1000; i++) {
System.out.println("main的i:"+i);
if (i==900){
//调用stop方法切换标志位，让线程停止
testStop.stop();
System.out.println("线程停止了");
}
}
}
}
线程休眠
- sleep(时间)指定当前线程组着的毫秒数
- sleep存在异常interruptedException;
- sleep时间达到后线程进入就绪状态
- sleep可以模拟网络延时，倒计时等
- 每一个对象都有一个锁，sleep不会释放锁
网络延时：
package com.xiaobai.thread.state;
import com.xiaobai.thread.lesson01.TestThread4;
//模拟网络延时---放大问题的发生性
public class TestSleep implements Runnable{
private int tickeNums = 10;
@Override
public void run() {
while (true){
if (tickeNums<=0){
break;
}
//模拟网络延时
try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+"---》拿到了第"+tickeNums--+"票");
}
}
public static void main(String[] args) {
TestSleep ticket = new TestSleep();
new Thread(ticket,"小明").start();
new Thread(ticket,"老师").start();
new Thread(ticket,"李三").start();
}
}
倒计时：
package com.xiaobai.thread.state;
import com.xiaobai.thread.lesson01.TestThread4;
//模拟网络延时---放大问题的发生性
public class TestSleep implements Runnable{
private int tickeNums = 10;
@Override
public void run() {
while (true){
if (tickeNums<=0){
break;
}
//模拟网络延时
try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+"---》拿到了第"+tickeNums--+"票");
}
}
public static void main(String[] args) {
TestSleep ticket = new TestSleep();
new Thread(ticket,"小明").start();
new Thread(ticket,"老师").start();
new Thread(ticket,"李三").start();
}
}
获取当前时间：
package com.xiaobai.thread.state;
import java.text.SimpleDateFormat;
import java.util.Date;
public class TestSleep3 {
//获取当前时间
public static void main(String[] args) {
Date startime = new Date(System.currentTimeMillis());
while (true){
try {
Thread.sleep(1000);
System.out.println(new SimpleDateFormat("HH:mm:ss").format(startime));
startime = new Date(System.currentTimeMillis());//更新时间
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
线程礼让
- 礼让线程，让抢钱正在执行的线程暂停，但不阻塞
- 将线程从运行状态转为就绪状态
- 让cpu重新调度，但礼让不一定成功，由CPU决定
package com.xiaobai.thread.state;
public class TestYield {
public static void main(String[] args) {
MyYield myYield = new MyYield();
new Thread(myYield,"a").start();
new Thread(myYield,"b").start();
}
}
class MyYield implements Runnable{
@Override
public void run() {
System.out.println(Thread.currentThread().getName()+"线程开始");
Thread.yield();
System.out.println(Thread.currentThread().getName()+"线程停止");
}
}
线程强制执行-join
待此线程执行完成后，再执行其他线程，其他线程阻塞
package com.xiaobai.thread.state;
//测试join
public class TestJoin implements Runnable{
@Override
public void run() {
for (int i = 0; i < 150; i++) {
System.out.println("线程VIP来了"+i);
}
}
public static void main(String[] args) throws InterruptedException {
TestJoin testJoin = new TestJoin();
Thread thread = new Thread(testJoin);
thread.start();
//主线程
for (int i = 0; i < 1000; i++) {
if (i==20){
thread.join();
}
System.out.println("main"+i);
}
}
}
线程状态
-
NEW
尚未启动的线程处于此状态
-
RUNNABLE
在Java虚拟机中执行的线程处于此状态
-
BLOCKED
被阻塞等待监视器锁定的线程处于此状态
-
WAITING
正在等待另一个线程执行特定动作的线程处于此状态
-
TIMED_WAITING
正在等待另一个线程执行动作达到指定等待时间的线程处于此状态
-
TERMINATED
已退出的线程处于此状态
线程观测
package com.xiaobai.thread.state;
//观察测试线程的状态
public class TestState {
public static void main(String[] args) {
Thread thread = new Thread(()->{
for (int i = 0; i < 5; i++) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("////////////////");
});
//观察状态
Thread.State state = thread.getState();
System.out.println(state);
//观察启动后
thread.start();
state = thread.getState();
System.out.println(state);
while (state != Thread.State.TERMINATED){
//只要线程不终止就有一直输出状态
try {
Thread.sleep(1000);
state = thread.getState();
System.out.println(state);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
线程优先级
设置优先级后，不一定优先级高的就先进行，只是分配了多的资源
package com.xiaobai.thread.state;
public class TestPriority {
public static void main(String[] args) {
//主线程默认优先级
System.out.println(Thread.currentThread().getPriority());
MyPriority myPriority = new MyPriority();
Thread t1 = new Thread(myPriority);
Thread t2 = new Thread(myPriority);
Thread t3 = new Thread(myPriority);
Thread t4 = new Thread(myPriority);
Thread t5 = new Thread(myPriority);
Thread t6 = new Thread(myPriority);
//先设置优先级，再启动
t1.start();
t2.setPriority(1);
t2.start();
t3.setPriority(4);
t3.start();
t4.setPriority(Thread.MAX_PRIORITY);
t4.start();
}
}
class MyPriority implements Runnable{
@Override
public void run() {
System.out.println(Thread.currentThread().getPriority());
}
}
守护(daemon)线程
- 线程分为用户线程和守护线程
- 虚拟机必须确保用户线程执行完毕
- 虚拟机不用等待守护线程执行完毕
- 如：后台记录操作日志，监控内存，垃圾回收等待。。
package com.xiaobai.thread.state;
public class TestDaemon {
public static void main(String[] args) {
God god = new God();
You you = new You();
Thread thread = new Thread(god);
thread.setDaemon(true);
thread.start();
new Thread(you).start();
}
}
class You implements Runnable{
@Override
public void run() {
for (int i = 0; i < 36500; i++) {
System.out.println("你一生都开心的或者");
}
System.out.println("=====bye");
}
}
class God implements Runnable{
@Override
public void run() {
while (true){
System.out.println("上帝保佑着你");
}
}
}
线程同步
并发
同一个对象被多个线程同时操作
队列
多个线程排队的等待池就是队列
锁机制synchronized
每个对象都有一个锁
弊端：性能下降。
三个安全问题案例
不安全的买票
package com.xiaobai.thread.syn;
//不安全的买票
//有负数，有买到同一张的
public class UnsafeBuyTicket {
public static void main(String[] args) {
BuyTicket buyTicket = new BuyTicket();
new Thread(buyTicket,"李四").start();
new Thread(buyTicket,"张三").start();
new Thread(buyTicket,"赵五").start();
}
}
class BuyTicket implements Runnable{
private int ticketNums = 10;
boolean flag =true;
@Override
public void run() {
//买票
while (flag){
try {
buy();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
private void buy() throws InterruptedException {
if (ticketNums<=0){
flag = false;
return;
}
Thread.sleep(1000);
System.out.println(Thread.currentThread().getName()+"买到了"+ticketNums--);
}
}
不安全的取钱
package com.xiaobai.thread.syn;
//不安全的取钱
public class UnsafeBank {
public static void main(String[] args) {
//创建账户
Account account = new Account(100,"结婚基金");
Drawing wo = new Drawing(account,50,"我");
Drawing ta = new Drawing(account,100,"她");
wo.start();
ta.start();
}
}
//账户
class Account{
int money; //余额
String name;//卡名
public Account(int money, String name) {
this.money = money;
this.name = name;
}
}
//银行取款
class Drawing extends Thread{
Account account;//账户
int drawingMoney;//取了多少钱
int nowMoney;//现在手里有多少钱
public Drawing(Account account,int drawingMoney,String name){
super(name);
this.account = account;
this.drawingMoney = drawingMoney;
}
@Override
public void run() {
if (account.money-drawingMoney<0){
System.out.println(Thread.currentThread().getName()+"钱不够，无法取出");
return;
}
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
account.money = account.money - drawingMoney;
nowMoney = nowMoney + drawingMoney;
System.out.println(Thread.currentThread().getName()+"账户余额为："+account.money);
//this.getName() = Thread.currentThread().getName() 因为继承了
System.out.println(this.getName()+"手里的钱："+nowMoney);
}
}
线程不安全的集合
package com.xiaobai.thread.syn;
import java.util.ArrayList;
import java.util.List;
//线程不安全的集合
public class UnsafeList {
public static void main(String[] args) {
List<String> list = new ArrayList<String>();
for (int i = 0; i < 10000; i++) {
new Thread(()->{
list.add(Thread.currentThread().getName());
}).start();
}
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(list.size());
}
}
同步方法
- synchronized方法和synchronized块
- synchronized方法控制对对象的访问
添加锁后的代码：
package com.xiaobai.thread.syn;
//不安全的买票
//有负数，有买到同一张的
public class UnsafeBuyTicket {
public static void main(String[] args) {
BuyTicket buyTicket = new BuyTicket();
new Thread(buyTicket,"李四").start();
new Thread(buyTicket,"张三").start();
new Thread(buyTicket,"赵五").start();
}
}
class BuyTicket implements Runnable{
private int ticketNums = 10;
boolean flag =true;
@Override
public void run() {
//买票
while (flag){
try {
buy();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
//synchronized 同步方法，锁的是this
private synchronized void buy() throws InterruptedException {
if (ticketNums<=0){
flag = false;
return;
}
Thread.sleep(1000);
System.out.println(Thread.currentThread().getName()+"买到了"+ticketNums--);
}
}
package com.xiaobai.thread.syn;
//不安全的取钱
public class UnsafeBank {
public static void main(String[] args) {
//创建账户
Account account = new Account(100,"结婚基金");
Drawing wo = new Drawing(account,50,"我");
Drawing ta = new Drawing(account,100,"她");
wo.start();
ta.start();
}
}
//账户
class Account{
int money; //余额
String name;//卡名
public Account(int money, String name) {
this.money = money;
this.name = name;
}
}
//银行取款
class Drawing extends Thread{
Account account;//账户
int drawingMoney;//取了多少钱
int nowMoney;//现在手里有多少钱
public Drawing(Account account,int drawingMoney,String name){
super(name);
this.account = account;
this.drawingMoney = drawingMoney;
}
@Override
public void run() {
synchronized (account){
if (account.money-drawingMoney<0){
System.out.println(Thread.currentThread().getName()+"钱不够，无法取出");
return;
}
//sleep可以放大问题的发生性
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
account.money = account.money - drawingMoney;
nowMoney = nowMoney + drawingMoney;
System.out.println(Thread.currentThread().getName()+"账户余额为："+account.money);
//this.getName() = Thread.currentThread().getName() 因为继承了
System.out.println(this.getName()+"手里的钱："+nowMoney);
}
}
}
package com.xiaobai.thread.syn;
import java.util.ArrayList;
import java.util.List;
//线程不安全的集合
public class UnsafeList {
public static void main(String[] args) {
//ArrayList 类是一个可以动态修改的数组
List<String> list = new ArrayList<String>();
for (int i = 0; i < 10000; i++) {
new Thread(()->{
synchronized (list){
list.add(Thread.currentThread().getName());
}
}).start();
}
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(list.size());
}
}
CopyOnWriteArrayList安全的数组集合
package com.xiaobai.thread.syn;
import java.util.concurrent.CopyOnWriteArrayList;
//测试JUC安全类型的集合
public class TestJUC {
public static void main(String[] args) {
CopyOnWriteArrayList<String> list = new CopyOnWriteArrayList<String>();
for (int i = 0; i < 10000; i++) {
new Thread(()->{
list.add(Thread.currentThread().getName());
}).start();
}
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(list.size());
}
}
死锁
产生条件：
- 互斥条件:一个资源每次只能被一个进程使用
- 请求与保持条件：一个进程因请求资源而阻塞时，对方已获得的资源保持不变
- 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
- 循环等待条件：若干进程之间形成一种头尾相接的循环等待
死锁案例：
package com.xiaobai.thread.syn;
//死锁：多个线程互相抱着对方需要的资源，形成僵持
public class DeadLock {
public static void main(String[] args) {
Makeup girl1 = new Makeup(0,"画画");
Makeup girl2 = new Makeup(1,"豆豆");
new Thread(girl1).start();
new Thread(girl2).start();
}
}
class Lipstick{
}
class Mirror{
}
class Makeup extends Thread{
//需要的资源只有一份，用static来保证只有一份
static Lipstick lipstick = new Lipstick();
static Mirror mirror = new Mirror();
int choice;
String name;//使用化妆品的人
public Makeup(int choice,String name){
this.choice=choice;
this.name = name;
}
@Override
public void run() {
//
try {
makeup();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//化妆方法
private void makeup() throws InterruptedException {
if (choice==0){
synchronized (lipstick){
System.out.println(this.name+"获得口红的锁");
Thread.sleep(1000);
synchronized (mirror){
System.out.println(this.name+"获得镜子的锁");
}
}
}else {
synchronized (mirror){
System.out.println(this.name+"获得镜子的锁");
Thread.sleep(2000);
synchronized (lipstick){
System.out.println(this.name+"获得口红的锁");
}
}
}
}
}
解决：
package com.xiaobai.thread.syn;
//死锁：多个线程互相抱着对方需要的资源，形成僵持
public class DeadLock {
public static void main(String[] args) {
Makeup girl1 = new Makeup(0,"画画");
Makeup girl2 = new Makeup(1,"豆豆");
new Thread(girl1).start();
new Thread(girl2).start();
}
}
class Lipstick{
}
class Mirror{
}
class Makeup extends Thread{
//需要的资源只有一份，用static来保证只有一份
static Lipstick lipstick = new Lipstick();
static Mirror mirror = new Mirror();
int choice;
String name;//使用化妆品的人
public Makeup(int choice,String name){
this.choice=choice;
this.name = name;
}
@Override
public void run() {
//
try {
makeup();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//化妆方法
private void makeup() throws InterruptedException {
if (choice==0){
synchronized (lipstick){
System.out.println(this.name+"获得口红的锁");
Thread.sleep(1000);
}
synchronized (mirror){
System.out.println(this.name+"获得镜子的锁");
}
}else {
synchronized (mirror){
System.out.println(this.name+"获得镜子的锁");
Thread.sleep(2000);
}
synchronized (lipstick){
System.out.println(this.name+"获得口红的锁");
}
}
}
}
LOCK(锁)
ReentrantLock类实现了Lock
package com.xiaobai.thread.syn;
import java.util.concurrent.locks.ReentrantLock;
public class TestLock {
public static void main(String[] args) {
TestLock2 testLock2 = new TestLock2();
new Thread(testLock2).start();
new Thread(testLock2).start();
new Thread(testLock2).start();
}
}
class TestLock2 implements Runnable{
int ticketNums = 10;
//定义lock锁
private final ReentrantLock lock = new ReentrantLock();
@Override
public void run() {
while (true){
try {
lock.lock();
if (ticketNums>=0){
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(ticketNums--);
}else {
break;
}
}finally {
lock.unlock();
}
}
}
}
线程协作
管程法
package com.xiaobai.thread.syn;
//测试：生产者消费者模型-->利用缓冲区解决：管程法
public class TestPC {
public static void main(String[] args) {
SynContainer container = new SynContainer();
new Productor(container).start();
new Consumer(container).start();
}
}
//生产者
class Productor extends Thread{
SynContainer container;
public Productor(SynContainer container){
this.container = container;
}
//生产
@Override
public void run() {
for (int i = 0; i < 100; i++) {
System.out.println("生产了"+i+"只鸡");
container.push(new Chicken(i));
}
}
}
//消费者
class Consumer extends Thread{
SynContainer container;
public Consumer(SynContainer container){
this.container = container;
}
@Override
public void run() {
for (int i = 0; i < 100; i++) {
container.pop();
System.out.println("消费了"+i+"只鸡");
}
}
}
class Chicken{
int id;//产品编号
public Chicken(int id) {
this.id = id;
}
}
//缓冲区
class SynContainer{
//需要一个容器大小
Chicken[] chickens = new Chicken[10];
//容器计数器
int count = 0;
//生产者放入产品
public synchronized void push(Chicken chicken){
//如果容器满了，就等待卖出
if (count== chickens.length){
//通知消费者消费，生产者等待
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//如果没有满，我们需要加入产品
chickens[count]=chicken;
count++;
//通知消费者消费
this.notifyAll();
}
public synchronized Chicken pop(){
//判断是否消费
if (count==0){
//等待生产者生产，消费者等待
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//如果可以消费
count--;
Chicken chicken = chickens[count];
//通知生产者生产
this.notifyAll();
return chicken;
}
}
信号灯法
package com.xiaobai.thread.syn;
//测试：
public class TestPC2 {
public static void main(String[] args) {
TV tv = new TV();
new Player(tv).start();
new Watcher(tv).start();
}
}
//生产者
class Player extends Thread{
TV tv;
public Player(TV tv){
this.tv = tv;
}
@Override
public void run() {
for (int i = 0; i < 20; i++) {
if (i%2==0){
this.tv.play("快乐大本营");
}else {
this.tv.play("极限挑战");
}
}
}
}
//消费者
class Watcher extends Thread{
TV tv;
public Watcher(TV tv){
this.tv = tv;
}
@Override
public void run() {
for (int i = 0; i < 20; i++) {
tv.watch();
}
}
}
//产品-->消费
class TV{
//演员表演，观众等待
//观众看，演员等待
String voice;
boolean flag = true;
//表演
public synchronized void play(String voice){
if (!flag){
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("演员表演了："+voice);
this.notifyAll();
this.voice = voice;
this.flag = !this.flag;
}
//观看
public synchronized void watch(){
if (flag){
try {
this.wait();
} catch (Exception e) {
e.printStackTrace();
}
}
System.out.println("观众观看了："+voice);
this.notifyAll();
this.flag = !this.flag;
}
}
线程池
package com.xiaobai.thread.syn;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class TestPool {
public static void main(String[] args) {
//创建线程池
ExecutorService service = Executors.newFixedThreadPool(10);
service.execute(new MyThread());
service.execute(new MyThread());
service.execute(new MyThread());
service.execute(new MyThread());
service.shutdown();
}
}
class MyThread implements Runnable{
@Override
public void run() {
System.out.println(Thread.currentThread().getName());
}
}
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