java线程创建

一、线程创建

1.三种创建方式

Thread类
Runnable接口
Callable接口

2.使用继承Thread类创建多线程

自定义类继承Thread类
重写run方法
调用start开启线程

//Thread类线程测试
//1.创建自定义类继承Thread
//2.重写run方法
//3.启动线程start
//线程启动后并不一定立即执行，需要cpu调度
public class TestThread1 extends Thread{
    //重写run方法
    @Override
    public void run() {
        for (int i = 0; i < 20; i++) {
            System.out.println("我不是主线程"+i);
            System.out.println(this.getId());
            System.out.println(this.getState());
        }
    }
    public static void main(String[] args) {
        TestThread1 testThread1 = new TestThread1();
        testThread1.start();
        for (int i = 0; i < 20; i++) {
            System.out.println("我是主线程"+i);
        }
    }
}

实例，用多线程实现网图的同时下载，使用commons.io包

import org.apache.commons.io.FileUtils;

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

//多线程实例，使用多线程同时下载多个网络图片
public class TestThread2 extends Thread{
    private String url;
    private String name;

    public TestThread2(String url, String name) {
        this.url = url;
        this.name = name;
    }
    //线程执行逻辑
    @Override
    public void run() {
        DownLoad downLoad = new DownLoad();
        downLoad.downLoad(url,name);
        System.out.println(name+"下载成功");
    }
    public static void main(String[] args) {
        TestThread2 t1 = new TestThread2("https://gitee.com/songping5201314/cloud-images/raw/master/img/image-20211120221646555.png","1.png");
        TestThread2 t2 = new TestThread2("https://gitee.com/songping5201314/cloud-images/raw/master/img/20200511193414_jyirh.jpg","src/2.jpg");
        TestThread2 t3 = new TestThread2("https://gitee.com/songping5201314/cloud-images/raw/master/img/image-20211208131014632.png ","src/3.jpg");
        t1.start();
        t2.start();
        t3.start();
    }
}
class DownLoad{
    public void downLoad(String url,String name){
        try {
            //默认的目录为项目的根目录
            FileUtils.copyURLToFile(new URL(url),new File(name));
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("downLoad方法有错误");
        }
    }
}

3.使用实现Runnable接口的方式实现多线程

//推荐使用这种方式创建多线程，因为一个实现了Runnable接口的对象可以同时被多个Thread线程使用，避免了单继承的局限性
public class TestThread3 implements Runnable{
    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            System.out.println("我不是主线程"+i);
        }
    }

    public static void main(String[] args) {
        TestThread3 testThread3 = new TestThread3();
        Thread thread=new Thread(testThread3);
        thread.start();//开启一个线程
        for (int i = 0; i < 100; i++) {
            System.out.println("我是主线程"+i);
        }
    }
}

4.线程的并发问题（不同步）

//多个线程同时对一个对象进行操作，产生资源的争夺，导致线程不安全
//模拟买票
public class TestThread4 implements Runnable{
    private int ticketnum=10;
    @Override
    public void run() {
        while(true){
            if (ticketnum==0){
                break;
            }
            try {
                Thread.sleep(200);//线程休眠0.2s
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+"买了第"+ticketnum--+"张票");//会出现数据的混乱，线程不安全，不同步 
        }
    }
    public static void main(String[] args) {
        TestThread4 testThread4 = new TestThread4();
        new Thread(testThread4,"刘备").start();
        new Thread(testThread4,"张飞").start();
        new Thread(testThread4,"关羽").start();
    }
}

5.模拟龟兔赛跑

//模拟龟兔赛跑
public class Race implements Runnable{
    //定义一个胜利者
    private String winner;
    @Override
    public void run() {
        for (int i = 0; i <= 100; i++) {
            //模拟兔子休眠，第49步停一次
            if (Thread.currentThread().getName().equals("兔子") && i==50){
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            boolean flag=gameOver(i);
            if (flag){
                break;
            }
            System.out.println(Thread.currentThread().getName()+"跑了"+i+"步");
        }
    }
    public boolean gameOver(int i){
        if (winner!=null){
            return true;
        }
        if (i>=100){
            winner=Thread.currentThread().getName();
            System.out.println("winner is"+Thread.currentThread().getName());
            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.通过Callable接口实现多线程

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：ExecutorServer ser=Executors.newFixedThreadPool(x);
提交执行：Future result1=ser.submit(t1);
获取结果：boolean r1=result1.get();//抛出异常
关闭服务：ser.shutdownNow();

import com.sun.org.apache.xpath.internal.operations.Bool;
import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.*;

//通过实现callable接口实现多线程下载网络图片
public class CallableTest implements Callable<Boolean> {
    @Override
    public Boolean call() throws Exception {
        DownLoad downLoad = new DownLoad();
        downLoad.downLoad(url,name);
        System.out.println(name+"下载成功");
        return true;
    }
    private String url;
    private String name;
    public CallableTest(String url, String name) {
        this.url = url;
        this.name = name;
    }
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        CallableTest t1 = new CallableTest("https://gitee.com/songping5201314/cloud-images/raw/master/img/image-20211120221646555.png","1.png");
        CallableTest t2 = new CallableTest("https://gitee.com/songping5201314/cloud-images/raw/master/img/20200511193414_jyirh.jpg","src/2.jpg");
        CallableTest t3 = new CallableTest("https://gitee.com/songping5201314/cloud-images/raw/master/img/image-20211208131014632.png ","src/3.jpg");
        //创建执行服务：
        ExecutorService ser= Executors.newFixedThreadPool(3);
         //提交执行：
        Future<Boolean> result1=ser.submit(t1);
        Future<Boolean> result2=ser.submit(t2);
        Future<Boolean> result3=ser.submit(t3);
         //获取结果：
        boolean r1=result1.get();//抛出异常
        boolean r2=result2.get();//抛出异常
        boolean r3=result3.get();//抛出异常
        // 关闭服务：
        ser.shutdownNow();
    }
}
class DownLoader{
    public void downLoad(String url,String name){
        try {
            FileUtils.copyURLToFile(new URL(url),new File(name));
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("downLoad方法有错误");
        }
    }
}

posted @ 2022-05-01 09:56 是韩信啊阅读(25) 评论(0) 编辑收藏举报

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java线程创建

一、线程创建

1.三种创建方式

2.使用继承Thread类创建多线程

3.使用实现Runnable接口的方式实现多线程

4.线程的并发问题（不同步）

5.模拟龟兔赛跑

6.通过Callable接口实现多线程

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