JAVA多任务与多进程

一、创建线程

1、继承Thread实现创建线程

自定义线程类继承Thread类

重写run()方法，编写线程执行体

创建线程对象，调用start()方法启动线程

//创建线程方式一：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() {
    
    
        for (int i = 0; i < 20; i++) {
    
    
            System.out.println("我在看代码---"+i);
        }
    }

    public static void main(String[] args) {
    
    
        //main主线程
        //创建一个线程对象
        TestThread1 testThread1 = new TestThread1();
        //调用start()方法开启线程
        testThread1.start();
        for (int i = 0; i < 200; i++) {
    
    
            System.out.println("我在学习多线程---"+i);
        }
    }
}

2、下载图片案例

首先需要在百度搜索commons-io的jar包，并导入lib下

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;
import java.net.URL;

//练习Thread，实现多线线程同步下载图片
public class ImageDownload extends Thread{
    
    
    private String url;
    private String name;
    public ImageDownload(String url, String name){
    
    
        this.url = url;  //网络图片地址
        this.name = name;  //保存的文件名称
    }

    @Override
    public void run() {
    
    
        WebDownloader webDownloader = new WebDownloader();
        try {
    
    
            webDownloader.downloader(url,name);
            System.out.println("下载的文件名为："+name);
        } catch (IOException e) {
    
    
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
    
    

        ImageDownload imageDownload1 = new ImageDownload("https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fwww.tutuzx.com%2Fd%2Ffile%2Ftitlepic%2F20210104%2F5aexbhmdkgq.jpg&refer=http%3A%2F%2Fwww.tutuzx.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1634471819&t=d3c1dac65f22edf5ca2d531721ac9e82","1.jpg");
        ImageDownload imageDownload2 = new ImageDownload("https://pics2.baidu.com/feed/43a7d933c895d14321b1075bdbc863055baf0747.jpeg?token=aa7eedf81a790c1dfe2871a3a076bafd&s=1C02137C4440D7475EA9F5EC0300302D","2.jpg");
        ImageDownload imageDownload3 = new ImageDownload("https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fi-1-lanrentuku.qqxzb-img.com%2F2020%2F12%2F23%2Fe64df5e8-95e1-4f9e-b47c-d6acb61c3ac5.jpg%3FimageView2%2F2%2Fw%2F1024%2F&refer=http%3A%2F%2Fi-1-lanrentuku.qqxzb-img.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1634471951&t=9a56af8617fe78b0160ded2921db070f","3.jpg");

        imageDownload1.start();
        imageDownload2.start();
        imageDownload3.start();
    }
}
class WebDownloader{
    
    
    public void downloader(String url,String name) throws IOException {
    
    
        FileUtils.copyURLToFile(new URL(url),new File(name));
    }
}

3、初识并发的问题

模拟车票购买，并发就是两个人会同时抢到同一张票
小白拿到了第10—张票
小明拿到了第9—张票
小黄拿到了第8—张票
小白拿到了第7—张票
小黄拿到了第7—张票
小明拿到了第7—张票
小明拿到了第6—张票
小黄拿到了第6—张票
小白拿到了第6—张票
小白拿到了第5—张票
小明拿到了第5—张票
小黄拿到了第5—张票
小明拿到了第4—张票
小黄拿到了第4—张票
小白拿到了第4—张票
小黄拿到了第3—张票
小白拿到了第1—张票
小明拿到了第2—张票

package com.geng.demo1;
//发现问题：多个线程同时操作一个资源，线程不安全，数据紊乱。
public class BuyTicket implements Runnable{
    
    

    private int ticketNums = 10;
    @Override
    public void run() {
    
    
        while (true){
    
    
            if(ticketNums <= 0){
    
    
                break;
            }
            //模拟延时
            try {
    
    
                Thread.sleep(200);
            } catch (InterruptedException e) {
    
    
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+"拿到了第"+ticketNums--+"---张票");
        }
    }

    public static void main(String[] args) {
    
    
        BuyTicket buyTicket = new BuyTicket();

        new Thread(buyTicket,"小明").start();
        new Thread(buyTicket,"小白").start();
        new Thread(buyTicket,"小黄").start();
    }
}

4、继承Thread创建多线程和实现Runnable创建多线程的区别

5、龟兔赛跑案例，巩固多线程

package com.geng.demo1;

public class Race implements Runnable{
    
    
    private static String winner;
    @Override
    public void run() {
    
    
        boolean flag;
        for (int i = 1; i <= 100 ; i++) {
    
    
            if(Thread.currentThread().getName().equals("兔子") && i % 10 == 0){
    
    
                try {
    
    
                    Thread.sleep(1);
                    System.out.println("兔子睡觉了");
                } catch (InterruptedException e) {
    
    
                    e.printStackTrace();
                }
            }
            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){
    
    
            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();
    }
}

6、实现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,sumbit(t1);

获取结果：

boolean r1 = result1.get()

关闭服务：

ser.shutdownNow();

仿照图片下载实现Callable接口

import java.io.IOException;
import java.util.concurrent.*;

//线程创建方式三：实现callable接口
//优点：可以获取返回值和抛出异常
public class TestCallable implements Callable {
    
    
    private String url;
    private String name;
    public TestCallable(String url, String name){
    
    
        this.url = url;
        this.name = name;
    }
    
    @Override
    public Boolean call() {
    
    
        WebDownloader webDownloader = new WebDownloader();
        try {
    
    
            webDownloader.downloader(url,name);
            System.out.println("下载的文件名为："+name);
        } catch (IOException e) {
    
    
            e.printStackTrace();
        }
        return true;
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
    
    

        TestCallable t1 = new TestCallable("https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fwww.tutuzx.com%2Fd%2Ffile%2Ftitlepic%2F20210104%2F5aexbhmdkgq.jpg&refer=http%3A%2F%2Fwww.tutuzx.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1634471819&t=d3c1dac65f22edf5ca2d531721ac9e82","4.jpg");
        TestCallable t2 = new TestCallable("https://pics2.baidu.com/feed/43a7d933c895d14321b1075bdbc863055baf0747.jpeg?token=aa7eedf81a790c1dfe2871a3a076bafd&s=1C02137C4440D7475EA9F5EC0300302D","5.jpg");
        TestCallable t3 = new TestCallable("https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fi-1-lanrentuku.qqxzb-img.com%2F2020%2F12%2F23%2Fe64df5e8-95e1-4f9e-b47c-d6acb61c3ac5.jpg%3FimageView2%2F2%2Fw%2F1024%2F&refer=http%3A%2F%2Fi-1-lanrentuku.qqxzb-img.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1634471951&t=9a56af8617fe78b0160ded2921db070f","6.jpg");

        //创建执行服务
        ExecutorService ser = Executors.newFixedThreadPool(3);
        
        //提交执行
        Future r1 = ser.submit(t1);
        Future r2 = ser.submit(t2);
        Future r3 = ser.submit(t3);
        
        //获取结果
        Boolean rs1 = (Boolean) r1.get();
        Boolean rs2 = (Boolean) r2.get();
        Boolean rs3 = (Boolean) r3.get();
        
        //关闭服务
        ser.shutdownNow();
    }
}

7、静态代理模式

利用静态代理模式思想，来解释实现Runnable接口的原理。

//静态代理模式总结：
//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做不了的事情
//真实对象可以专注做自己的事情
public class StaticProxy {
    
    
    public static void main(String[] args) {
    
    
        WeddingCompany a = new WeddingCompany(new You());
        a.HappyMarry();
    }
}
interface Marry{
    
    
    void HappyMarry();
}
class You implements Marry{
    
    
    @Override
    public void HappyMarry() {
    
    
        System.out.println("秦老师要结婚了，超开心");
    }
}
class WeddingCompany implements Marry{
    
    
    private Marry target;

    public WeddingCompany(Marry target) {
    
    
        this.target = target;
    }

    @Override
    public void HappyMarry() {
    
    
        before();
        this.target.HappyMarry();
        after();
    }
    public void before(){
    
    
        System.out.println("结婚之前布置现场");
    }
    public void after(){
    
    
        System.out.println("结婚之后收尾款");
    }
}

8、Lamda表达式

public class TestLambda {
    
    
    //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) {
    
    
        Like2 like = new Like2();
        like.Lambda();

        Like like1 = new Like();
        like1.Lambda();

        //局部内部类
        class Like3 implements ILike{
    
    
            @Override
            public void Lambda() {
    
    
                System.out.println("I like lambda3");
            }
        }
        Like3 like3 = new Like3();
        like3.Lambda();

        //匿名内部类，没有类的名称，必须借助接口或者父类
        ILike like4 = new ILike() {
    
    
            @Override
            public void Lambda() {
    
    
                System.out.println("I like lambda4");
            }
        };
        like4.Lambda();
        //用lambda简化
        ILike like5 = ()->{
    
    
            System.out.println("I like lambda5");
        };
        like5.Lambda();
        //lambda简化，去大括号
        like5 = () -> System.out.println("shuchu");
    }
}
//总结：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
        //前提是接口为函数式接口
//多个参数也可以去掉参数类型，要去就都去掉，必须加上括号；
interface ILike{
    
    
    void Lambda();
}
class Like implements ILike{
    
    
    @Override
    public void Lambda() {
    
    
        System.out.println("I like lambda");
    }
}

二、线程状态

创建状态

就绪状态

运行状态

阻塞状态

死亡状态

1、线程停止

//测试stop
//1、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destroy等过时或者JDK不建议使用的方法
public class TestStop implements Runnable {
    
    

    //1、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"+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");
            }
        }
    }
}

2、线程休眠

import java.text.SimpleDateFormat;
import java.util.Date;

//模拟网络延时:放大问题的发生性，见网络购票
//模拟倒计时
public class TestSleep {
    
    

    public static void main(String[] args) throws InterruptedException {
    
    
        //打印当前系统时间
        Date date = new Date(System.currentTimeMillis());  //获取当前系统时间
        while (true){
    
    
            System.out.println(new SimpleDateFormat("HH:mm:ss").format(date));
            Thread.sleep(1000);
            date = new Date(System.currentTimeMillis());  //更新系统时间
        }
    }

3、线程礼让—yield

//测试礼让线程
//礼让不一定成功，看CPU心情
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");
    }
}

a线程开始执行
b线程开始执行
b线程停止执行
a线程停止执行

4、线程强制执行——JOIN

//测试JOIN方法，想插队
public class TestJoin implements Runnable{
    
    

    @Override
    public void run() {
    
    
        try {
    
    
            Thread.sleep(1000);
        } catch (InterruptedException e) {
    
    
            e.printStackTrace();
        }
        for (int i = 0; i < 1000; 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();  //执行插队
            }
            System.out.println("main"+i);
        }
    }
}

5、观测线程状态

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("//");
        });
        //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);

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

6、线程的优先级

//测试线程的优先级
public class TestPriority {
    
    

    public static void main(String[] args) {
    
    

        //主线程默认优先级
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());

        MyPriority myPriority = new MyPriority();

        Thread thread1 = new Thread(myPriority);
        Thread thread2 = new Thread(myPriority);
        Thread thread3 = new Thread(myPriority);
        Thread thread4 = new Thread(myPriority);

        //先设置优先级，再启动
        thread1.setPriority(1);
        thread1.start();

        thread2.setPriority(1);
        thread2.start();

        thread3.setPriority(1);
        thread3.start();

        thread4.setPriority(Thread.MAX_PRIORITY);
        thread4.start();
    }
}

class MyPriority implements Runnable{
    
    

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

7、守护线程

//测试守护线程
public class TestDaemon {
    
    

    public static void main(String[] args) {
    
    
        God god = new God();
        You1 you1 = new You1();

        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(); //启动守护线程

        new Thread(you1).start();  //启动用户线程
    }
}

class God implements Runnable{
    
    

    @Override
    public void run() {
    
    
        while (true){
    
    
            System.out.println("上帝护佑你！");
        }
    }
}

class You1 implements Runnable{
    
    
    @Override
    public void run() {
    
    
        for (int i = 0; i < 356; i++) {
    
    
            System.out.println("你一生活得都开心");
        }
        System.out.println("===========goodbye world!==========");
    }
}

8、同步方法及代码块

//测试守护线程
public class TestDaemon {
    
    

    public static void main(String[] args) {
    
    
        God god = new God();
        You1 you1 = new You1();

        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(); //启动守护线程

        new Thread(you1).start();  //启动用户线程
    }
}

class God implements Runnable{
    
    

    @Override
    public void run() {
    
    
        while (true){
    
    
            System.out.println("上帝护佑你！");
        }
    }
}

class You1 implements Runnable{
    
    
    @Override
    public void run() {
    
    
        for (int i = 0; i < 356; i++) {
    
    
            System.out.println("你一生活得都开心");
        }
        System.out.println("===========goodbye world!==========");
    }
}

//发现问题：多个线程同时操作一个资源，线程不安全，数据紊乱。
class Tickets{
    
    
    private int ticketNums = 10;

    public int getTicketNums() {
    
    
        return ticketNums;
    }

    public void setTicketNums(int ticketNums) {
    
    
        this.ticketNums = ticketNums;
    }
}

public class BuyTicket implements Runnable{
    
    

    Tickets  tickets = new Tickets();  //票数
    int ticketNums = tickets.getTicketNums();
    @Override
    public void run() {
    
    
        while (true){
    
    
            try {
    
    
                Thread.sleep(200);
            } catch (InterruptedException e) {
    
    
                e.printStackTrace();
            }
            synchronized (tickets){
    
     //()中放的是需要操作的资源对象，synchronized默认是run方法
                if(ticketNums <= 0){
    
    
                    break;
                }
                try {
    
    
                    Thread.sleep(200);
                } catch (InterruptedException e) {
    
    
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName()+"拿到了第"+ticketNums--+"---张票");
            }
        }
    }

    public static void main(String[] args) {
    
    
        BuyTicket buyTicket = new BuyTicket();

        new Thread(buyTicket,"小明").start();
        new Thread(buyTicket,"小白").start();
        new Thread(buyTicket,"小黄").start();
    }
}

已完结