多线程小练习----下载图片，买火车票，龟兔赛跑

缺乏、安全感 2022-10-09 06:17 116阅读 0赞

**练习thread实现多线程下载图片**

public class TestThread02 extends Thread{
        
        private String url;
        private String name;
        public TestThread02(String url,String name){
        
            this.url = url;//图片地址
            this.name = name;//文件名
        }
        //下载图片线程执行体
        @Override
        public void run() {
        
            WebDownLoader webDownLoader = new WebDownLoader();//创建下载器对象
            webDownLoader.downloader(url,name);//调用下载方法
            System.out.println("下载了文件名为："+name);
        }
        public static void main(String[] args) {
        
            TestThread02 t1 = new TestThread02("https://ns-strategy.cdn.bcebos.com/ns-strategy/upload/fc_big_pic/part-00391-2414.jpg","1.jpg");
            TestThread02 t2 = new TestThread02("https://ss1.bdstatic.com/70cFuXSh_Q1YnxGkpoWK1HF6hhy/it/u=2683597247,2042643916&fm=11&gp=0.jpg","2.jpg");
            TestThread02 t3 = new TestThread02("https://ss1.bdstatic.com/70cFvXSh_Q1YnxGkpoWK1HF6hhy/it/u=954496120,1621506021&fm=26&gp=0.jpg","3.jpg");
            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();
            }
        }
    }

**初识并发问题**

> 当多个线程对象对同一个资源进行操作则会造成并发问题

**买火车票的例子**

//模拟多个线程同时操作一个对象
    //买火车票的例子
    //发现问题：多个线程操作同一个资源的情况下，线程不安全，数据紊乱
    public class TestThread04 implements Runnable{
        
    
        private int ticketNums = 10;//票数
        @Override
        public void run() {
        
            while (true){
        
                if (ticketNums<=0){
        
                    break;
                }
                //模拟延时
                try {
        
                    Thread.sleep(200);
                } catch (InterruptedException e) {
        
                    e.printStackTrace();
                }
                //Thread.currentThread().getName()：获取线程名字
                System.out.println(Thread.currentThread().getName()+"拿到了第"+ticketNums--+"张票");
            }
        }
        public static void main(String[] args) {
        
            TestThread04 thread04 = new TestThread04();
            new Thread(thread04,"小梅").start();
            new Thread(thread04,"小姚").start();
            new Thread(thread04,"黄牛党").start();
        }
    }

**模拟龟兔赛跑**

public class Race implements Runnable{
        
        //胜利者
        private static String winner;
    
        //1.首先来个赛道距离，然后要离终点越来越近
        @Override
        public void run() {
        
            for (int i = 1; i <= 100; i++) {
        
    
                //5.故事中时乌龟赢的，兔子需要睡觉觉，所以我们来模拟兔子睡觉
                if (Thread.currentThread().getName().equals("兔子") && i%10==0){
        
                    try {
        
                        Thread.sleep(10);
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                }
    
                // 2.判断比赛是否结束
                boolean flag=gameOver(i);
                if (flag){
        
                    break;
                }
    
                System.out.println(Thread.currentThread().getName()+"跑了"+i+"步");
    
            }
        }
        //判断比赛是否完成
        public boolean gameOver(int mi){
        
            //判断胜利者
            if (winner!=null){
        
                return true;
            }{
        //省略了else if()
                if (mi>=100){
        
                    winner=Thread.currentThread().getName();
                    System.out.println("冠军是"+winner);
                    return true;
                }
            }
            return false;
        }
    
        public static void main(String[] args) {
        
            // 4.龟兔赛跑开始
            Race race = new Race();
    
            new Thread(race,"乌龟").start();
            new Thread(race,"兔子").start();
    
        }
    }