Java线程

线程实现【重点】

• 线程名字

  //主线程定义线程名字并启动
  new Thread(testThread5,"销售A").start();
              
  //线程内获取当前线程名字
  Thread.currentThread().getName()

Thread

//创建线程的方式一：继承Thread类，重写run()方法，调用start开启线程
public class TestThread1 extends Thread{

    @Override
    public void run() {
        //run方法线程体
        for (int i = 0; i < 200; i++) {
            System.out.println("我在看代码---" + i);
        }
    }

    //main线程，主线程
    public static void main(String[] args) {
        
        //创建一个线程对象
        TestThread1 testThread1=new TestThread1();

        //调用 start() 方法开启线程:同时运行，交替执行
        testThread1.start();

        //调用 run() 方法先跑线程
        //testThread1.run();

        for (int i = 0; i < 200; i++) {
            System.out.println("我在学习多线程--");
        }
    }
     
}

注意

• 继承Thread类，重写run()方法，调用start开启线程
• 线程开启不一定立即执行，由cpu调度执行
• java单继承，继承Thread无法继承其他类

• 练习 – 使用多线程同时下载多张图片案例

//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;
    }

    //下载图片线程的执行体
    @Override
    public void run() {
        WebDownloader webDownloader=new WebDownloader();
        webDownloader.downloader(url,name);
        System.out.println("下载了文件名为："+name);
    }

    public static void main(String[] args) {
        TestThread2 t1 = new TestThread2("https://chen-131.png","1.png");
        TestThread2 t2 = new TestThread2("https://chen-131.jpg","2.jpg");
        TestThread2 t3 = new TestThread2("https://chen-131.png","3.png");

        t1.start();
        t2.start();
        t3.start();
    }
}


//下载器
class WebDownloader{
    //下载方法
    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");
        }
    }
}

下载 – 导包 – commons-io

---

Runnable【*】

• 实现 Runnable 接口
• 实现 run() 方法
• 创建 Thread 对象 来开启 start() 线程

//创建线程方法2：实现runable接口，重写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 < 200; i++) {
            System.out.println("我在看代码---" + i);
        }
    }


    public static void main(String[] args) {

        //创建runnable接口的实现类对象
        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();
         
        new Thread(testThread3).start();

        for (int i = 0; i < 1000; i++) {
            System.out.println("我在学习多线程--" + i);
        }
    }
}

• 练习 – 使用多线程同时下载多张图片

//和继承Thread类使用方法基本一致。只不过是启动线程需要改变

     new Thread(t1).start();
     new Thread(t2).start();
     new Thread(t3).start();

• 龟兔赛跑案例

//模拟龟兔赛跑
public class Race implements Runnable {

    //胜利者
    private static String winner;

    @Override
    public void run() {
        for (int i = 1; i <= 100; i++) {

            //模拟兔子休息
            if (Thread.currentThread().getName().equals("兔子")&&i%10==0){
                try {
                    Thread.sleep(2);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }

            //判断比赛是否结束
            boolean flag = gameOver(i);
            //比赛结束，停止程序
            if (flag){
                break;
            }
            System.out.println(Thread.currentThread().getName()+"-->跑了"+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){//已经存在胜利者了
            return true;
        }else {
            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();
    }
}

---

小结

---

Callable

• 线程创建方式三：实现callable接口

• callable的好处

  • 1.可以定义返回值
  • 2.可以抛出异常

public class TestCallabel implements Callable {

    private String url;
    private String name;

    public TestCallabel(String url,String name){
        this.url=url;
        this.name=name;
    }

    //下载图片线程的执行体
    @Override
    public Boolean call() {
        WebDownloader webDownloader=new WebDownloader();
        webDownloader.downloader(url,name);
        System.out.println("下载了文件名为："+name);
        return true;
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        TestCallabel t1 = new TestCallabel("https://chen-1.png","1.png");
        TestCallabel t2 = new TestCallabel("https://chen-1.jpg","2.jpg");
        TestCallabel t3 = new TestCallabel("https://chen-1.png","3.png");

        //创建执行服务
        ExecutorService service = Executors.newFixedThreadPool(3);

        //提交执行
        Future<Boolean> r1 = service.submit(t1);
        Future<Boolean> r2 = service.submit(t2);
        Future<Boolean> r3 = service.submit(t3);

        //获取结果
        boolean rs1 = r1.get();
        boolean rs2 = r2.get();
        boolean rs3 = r3.get();

        System.out.println(rs1);
        System.out.println(rs2);
        System.out.println(rs3);

        //关闭服务
        service.shutdownNow();

    }
}


//下载器
class WebDownloader{
    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");
        }
    }
}

Lambda表达式

• 函数式接口
  • 只有一个抽象方法

• 原写法

public class TestLambdal {
    public static void main(String[] args) {
        ILike iLike = new Like();
        iLike.lambda();
    }
}

//1.定义一个函数式接口
interface ILike{
    void lambda();
}

//2.实现类
class Like implements  ILike{
    @Override
    public void lambda() {
        System.out.println("I Like Lambda");
    }
}

• 推导lambda写法

public class TestLambdal {
    public static void main(String[] args) {
        //用Lambda简化
        ILike iLike = () ->{
            System.out.println("I Like Lambda5");
        };
        iLike.lambda();
    }
}

定义一个函数式接口
interface ILike{
    void lambda();
}

• 简化写法

public class TestLambda2 {

    public static void main(String[] args) {
        //lambda
        CP cpe=null;

         //原型
        cpe=(int a)->{
            System.out.println("lambda ： cpe-->" + a);
        };

        //简化1.去除参数类型 ------------  推荐  -----------------------------
        cpe = (a)->{
            System.out.println("lambda ： cpe-->" + a);
        };

        //简化2.简化括号 
        cpe = a -> {
            System.out.println("lambda ： cpe-->" + a);
        };

        //简化3.去掉花括号
        cpe = a-> System.out.println("lambda ： cpe-->" + a);

    }
}

interface CP{
    void  cpe(int a);
}

总结：

• lambada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

• 前提是接口为函数式接口

• 多个参数也可以去掉参数类型，要去掉就都去掉，必须加上括号(a,b)，

---

线程状态

观察线程状态

public class TestState {
    public static void main(String[] args) throws InterruptedException {
        Thread thread = new Thread(() -> {
            for (int i = 0; i < 5; i++) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            System.out.println("//////");
        });

        //获取线程状态
        Thread.State state = thread.getState();
        System.out.println(state);  //输出为：NEW


        //观察启动
        thread.start();//启动线程
        state = thread.getState();
        System.out.println(state);//输出为：RUN

        while (state != Thread.State.TERMINATED) {
            //只要线程不终止，就一直输出状态
            Thread.sleep(100);
            state = thread.getState();//更新线程状态
            System.out.println(state);//输出状态
        }
    }
}

线程停止 –stop

1.建议线程正常停止 —–> 利用次数，不建议死循环

2.建议使用标志位 –> 设置一个标志位

3.不要使用 stop 或者 destroy 等过时或者JDK不建议使用的方法

public class TestTop implements Runnable{

    //1.设置一个标识位
    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) {
         
        TestTop testTop = new TestTop();
        new Thread(testTop).start();

        for (int i = 0; i < 1000; i++) {
            System.out.println("main  "+i);
            if (i==900){
                //调用stop方法切换标志位，让线程停止
                testTop.stop();
                System.out.println("该线程停止了");
            }
        }
    }
}

线程休眠–sleep

//主线程打印当前系统时间
Date startTime = new Date(System.currentTimeMillis());//获取系统当前时间
while (true){
     try {
          Thread.sleep(1000);
          System.out.println(new SimpleDateFormat("HH:mm:ss").format(startTime));
          startTime = new Date(System.currentTimeMillis());//更新当前时间
     } catch (InterruptedException e) {
          e.printStackTrace();
     }
}

线程礼让–yield

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()+"线程开始执行");
        Thread.yield();//礼让
        System.out.println(Thread.currentThread().getName()+"线程停止执行");
    }
}

合并线程–join

• Join合并线程，待此线程执行完成后，再执行其他线程，其他线程阻塞
• 插队

public class TestJoin implements Runnable{
    @Override
    public void run() {
        try {
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        for (int i = 0; i < 100; i++) {
            System.out.println("线程vip来了"+i);
        }
    }

    public static void main(String[] args) throws InterruptedException {
        //启动我们的线程
        TestJoin testJoin = new TestJoin();
        Thread thread = new Thread(testJoin);
        thread.start();

        //主线程
        for (int i = 0; i < 1000; i++) {
            if (i==200){
                thread.join();//插队
            }
            System.out.println("man  "+i);
        }
    }
}

线程优先级–priority

• 先设置优先级，再启动

public class TestPriority {
    public static void main(String[] args) {
        //主线程优先级--5
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());

        MyPrority myPrority = new MyPrority();

        Thread t1 = new Thread(myPrority);
        Thread t2 = new Thread(myPrority);
        Thread t3 = new Thread(myPrority);
        Thread t4 = new Thread(myPrority);
        Thread t5 = new Thread(myPrority);
        Thread t6 = new Thread(myPrority);

        //先设置优先级，再启动
        t1.start();

        t2.setPriority(2);
        t2.start();

        t3.setPriority(6);
        t3.start();

        t4.setPriority(Thread.MAX_PRIORITY);
        t4.start();

        t5.setPriority(Thread.MIN_PRIORITY);
        t5.start();

        t6.setPriority(1);
        t6.start();


    }
}

class MyPrority implements Runnable{

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());
    }
}

守护线程–daemon

• 即 守护线程 会**陪伴 **被守护的线程 执行完毕

• //true则设置为守护线程
  //默认是false表示是用户线程，正常的线程都是用户线程
   thread.setDaemon(true);
    
  
  ```java
  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);//默认是false表示是用户线程，正常的线程都是用户线程
  
          thread.start();//保护线程启动
  
          new Thread(you).start();//用户线程启动
      }
  }
  
  //守护线程
  class God implements Runnable{
  
      @Override
      public void run() {
          while (true){
              System.out.println("保护着你");
          }
      }
  }
  
  //被守护的线程
  class You implements Runnable{
  
      @Override
      public void run() {
          for (int i = 0; i < 36500; i++) {
              System.out.println("开心");
          }
          System.out.println("==================bye====================");
      }
  }
  

---

线程同步【重点】

并发

• 多个线程操作同一个资源
• 等待机制 – 对象等待池

安全集合CopyOnWriteArrayList

不需要锁，各线程排队进行

//测试JUC安全类型的集合
public class TestJUC {
    public static void main(String[] args) throws InterruptedException {
        CopyOnWriteArrayList<String> list = new CopyOnWriteArrayList();
        for (int i = 0; i < 1000; i++) {
            new Thread(()->{
                list.add(Thread.currentThread().getName());
            }).start();
        }
        Thread.sleep(100);
        System.out.println(list.size());
    }
}

锁机制 – synchronized

synchronized方法

锁 类本身 private synchronized void buy(){ }

public class UnsafeBuyTicket {
    public static void main(String[] args) {
        BuyTicket station = new BuyTicket();

        new Thread(station,"A员工").start();
        new Thread(station,"B员工").start();
        new Thread(station,"C员工").start();

    }
}

class BuyTicket implements Runnable{

    private int ticketNums = 10;
    boolean flag = true;

    @Override
    public void run() {
        //买票
        while (flag){
            buy();
            //模拟延时
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    //synchronized  同步方法，锁的是this
    private synchronized void buy(){
        //判断是否有票
        if (ticketNums<=0){
            flag=false;
            return;
        }
        //买票
        System.out.println(Thread.currentThread().getName()+"拿到"+ticketNums--);
    }
}

synchronized块

• 可以锁任意对象 synchronized (account){ }
• 锁的对象：变化的量，需要增删改的量

package com.synchronizedc;

//不安全的取钱
//两人取，账户
public class UnsafeBank {
    public static void main(String[] args) {
        //账户
        Account account = new Account(1000,"结婚基金");

        Drawing you = new Drawing(account,50,"你");
        Drawing girlFirend = new Drawing(account,100,"girlFirend");
        girlFirend.start();
        you.start();
    }
}

//账号
class  Account{
    int money;
    String name;
    public Account(int money, String name) {
        this.money = money;
        this.name = name;
    }
}

//银行：模拟取款
class  Drawing extends Thread{
    Account account;//账号
    //取多少钱
    int drawingMoney;
    //手里
    int nowMoney;

    public Drawing(Account account,int drawingMoney,String name){
        super(name);
        this.account=account;
        this.drawingMoney=drawingMoney;
    }

    //取钱
    //synchronized 默认锁this

    @Override
    public  void run() {
        synchronized (account){

            //判断有没有钱
            if (account.money-drawingMoney<0){
                System.out.println(Thread.currentThread().getName()+"不够，取不了");
                return;
            }

            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            //余额
            account.money=account.money-drawingMoney;

            //手里的钱
            nowMoney=nowMoney+drawingMoney;

            System.out.println(account.name+"余额为:"+account.money);
            //Thread.currentThread().getName()==this.getName()
            System.out.println(this.getName()+"手里的钱："+nowMoney);
        }

    }
}

死锁

• 多个线程互相抱着对方需要的资源，然后形成僵持

• 使用 synchronized块 上锁和解锁

//死锁：多个线程互相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 g1 = new Makeup(0,"灰姑凉");
        Makeup g2 = new Makeup(1,"白雪公主");
        g1.start();
        g2.start();
    }
}

//口红
class  Lipstick{

}

//镜子
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;//选择
    String girlName;//使用化妆品的人

    Makeup(int choice, String girlName) {
        this.choice = choice;
        this.girlName = girlName;
    }

    @Override
    public void run() {
        //化妆
        try {
            makeup();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }

    //化妆，互相持有对方的锁，就是需要拿到对方的资源
    private void makeup() throws InterruptedException {
        if (choice == 0) {
            synchronized (lipstick) {//获得口红的锁
                System.out.println(this.girlName + "获得口红的锁");
                Thread.sleep(1000);
            }

            synchronized (mirror) {//一秒后获取镜子的锁
                System.out.println(this.girlName + "获得镜子的锁");
            }
        }else {
            synchronized (mirror) {//获得镜子的锁
                System.out.println(this.girlName + "获得镜子的锁");
                Thread.sleep(2000);
            }

            synchronized (lipstick) {//2秒后获取口红的锁
                System.out.println(this.girlName + "获得口红的锁");
            }
        }
    }
}

Lock（锁）

• ReentrantLock

• 定义：private final ReentrantLock lock = new ReentrantLock();
• 在 try 中上锁，finally 中解锁
• 显式锁，手动开启和关闭
• 

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();//加锁
                if (ticketNums>0){
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(ticketNums--);
                }else {
                    break;
                }
            }finally {
                lock.unlock();//解锁
            }

        }
    }
}

总结：

---

线程通信问题

生产者消费者模式

管程法

//生产者消费者模型 -->  利用缓冲区解决：管程法

//生产者  ，  消费者   ，  产品  ，  缓冲区
public class TestPC {
    public static void main(String[] args) {
        SyncContainer container=new SyncContainer();

        new Productor(container).start();
        new Consumer(container).start();
    }
}

//生产者
class Productor extends Thread{
    SyncContainer container;

    public Productor(SyncContainer container){
        this.container=container;
    }

    //生产
    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {

            container.push(new Chicken(i));
            System.out.println("生产了"+i+"只鸡");
        }
    }
}

//消费者
class  Consumer extends Thread{
    SyncContainer container;

    public Consumer(SyncContainer container){
        this.container=container;
    }

    //消费

    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            System.out.println("消费了-->"+container.pop().id+"只鸡");
        }
    }
}

//产品
class Chicken{
    int id ;//产品编号

    public Chicken(int id) {
        this.id = id;
    }
}

//缓冲区
class SyncContainer{

    //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，就需要等待消费者消费
        if (count==chickens.length){
            //通知消费者消费，生产等待
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        //如果没有满，我们就需要丢入产品
        chickens[count]=chicken;
        count++;

        //可以通知消费者消费了
        this.notifyAll();
    }

    //消费者消费产品
    public synchronized Chicken pop(){
        //判断能否消费
        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];

        //吃完了，通知生产者生产
        this.notifyAll();
        return chicken;
    }

}

信号灯法

//生产消费者模式：信号灯法，标志位解决
public class TestPC2 {
    public static void main(String[] args) {
        TV tv = new TV();
        new Player(tv).start();
        new Watcher(tv).start();
    }
}

//生产者-->演员
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("快乐大本营播放中");
            }else {
                this.tv.play("抖音：记录美好生活");
            }
        }
    }
}

//消费者-->观众
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-->节目
class TV{
    //演员表演，观众等待
    //观众观看，演员等待
    String voice;//表演的节目
    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);
        //通知观众观看
        this.notifyAll();//通知唤醒
        this.voice=voice;
        this.flag=!this.flag;
    }

    //观看
    public synchronized void watch(){
        if (flag){
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println("观看了："+voice);
        //通知演员表演
        this.notifyAll();
        this.flag=!this.flag;
    }
}

---

线程池

//线程池
public class TestPool {

    public static void main(String[] args) {
        //1.创建服务，创建线程池
        //newFixedThreadPool  参数为：线程池的大小
        ExecutorService service = Executors.newFixedThreadPool(10);

        service.execute(new MyThread());
        service.execute(new MyThread());
        service.execute(new MyThread());
        service.execute(new MyThread());
        service.execute(new MyThread());

        //2.关闭连接
        service.shutdownNow();
    }
}

class MyThread implements Runnable{

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName());
    }
}