文章

线程创建方式

发表于
作者 Sylvan
5 分钟阅读

线程

  • 一个进程中若开辟多个线程，线程的运行由调度器控制，先后顺序不能人为干预。

  • 实现方式

    1. 继承 Thread类

      • 调用run方法，只有主线程一条路

      • 调用start方法，主线程和子线程并行交替执行

      • 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23

        public class MyThread extends Thread{
       
    @Override
    public void run() {
        for (int i = 0; i < 20; i++) {
            System.out.println("xixi");
        }
    }
       
    public static void main(String[] args) {
       
        MyThread myThread = new MyThread();
        //myThread.run();只有主线程一条路，先xixi后haha
        //开启线程，不一定立刻执行，由cpu调度
        myThread.start();//同时运行，xixi、haha交替
       
        //main线程
        for (int i = 0; i < 20; i++) {
            System.out.println("haha");
        }
    }
       
}

      • 导入common-io.jar下载图片

        1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47

        import org.apache.commons.io.FileUtils;
       
import java.io.File;
import java.io.IOException;
import java.net.URL;
       
public class MyThread2 extends Thread{
       
    private String url;
    private String name;
       
    public MyThread2(String url, String name){
        this.name = name;
        this.url = url;
    }
       
    @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) {
        MyThread2 t1 = new MyThread2("https://ss0.bdstatic.com/70cFuHSh_Q1YnxGkpoWK1HF6hhy/it/u=3246675119,2528014287&fm=26&gp=0.jpg", "csgo1.jpg");
        MyThread2 t2 = new MyThread2("https://ss0.bdstatic.com/70cFuHSh_Q1YnxGkpoWK1HF6hhy/it/u=3246675119,2528014287&fm=26&gp=0.jpg", "csgo2.jpg");
        MyThread2 t3 = new MyThread2("https://ss0.bdstatic.com/70cFuHSh_Q1YnxGkpoWK1HF6hhy/it/u=3246675119,2528014287&fm=26&gp=0.jpg", "csgo3.jpg");
       
        t1.start();
        t2.start();
        t3.start();
       
    }
}
       
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("downloader异常");
        } finally {
        }
    }
}

    2. 实现Runnable接口

      • 推荐使用，避免单继承局限性，灵活方便，方便同一个对象被多个线程使用

      1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

        public class MyThread3 implements Runnable{
      @Override
      public void run() {
          for (int i = 0; i < 20; i++) {
              System.out.println("xixi");
          }
      }
       
      public static void main(String[] args) {
       
          //创建实现runnable接口的类对象
          MyThread3 myThread3 = new MyThread3();
          //创建线程对象，通过线程对象启动线程，代理
          new Thread(myThread3).start();
       
       
          for (int i = 0; i < 20; i++) {
              System.out.println("haha");
          }
      }
  }

      • 多线程同时操作一个对象

        1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46

               
public class Application {
    public static void main(String[] args) {
        MyThread4 myThread4 = new MyThread4();
        new Thread(myThread4, "ThreadA").start();
        new Thread(myThread4, "ThreadB").start();
        new Thread(myThread4, "ThreadC").start();
       
    }
}
       
class MyThread4 implements Runnable{
       
    private int ticketNumbs = 10;
       
    @Override
    public void run() {
        while (true){
            if(ticketNumbs <= 0)
                break;
       
            // 模拟延时
            try {
                Thread.sleep(20);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "拿到了第" + ticketNumbs-- + "张票");
        }
    }
}
/**
 * ThreadA拿到了第9张票
 * ThreadB拿到了第8张票
 * ThreadC拿到了第10张票
 * ThreadB拿到了第7张票
 * ThreadA拿到了第7张票
 * ThreadC拿到了第6张票
 * ThreadA拿到了第5张票
 * ThreadB拿到了第4张票
 * ThreadC拿到了第3张票
 * ThreadA拿到了第2张票
 * ThreadB拿到了第1张票
 * ThreadA拿到了第0张票
 * ThreadC拿到了第0张票
 */

    3. 实现Callable接口

      • 可以定义返回值、可以抛出异常

      • 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61

        import org.apache.commons.io.FileUtils;
       
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.*;
       
class MyCallable implements Callable<Boolean> {
       
    private String url;
    private String name;
       
    public MyCallable(String url, String name) {
        this.name = name;
        this.url = url;
    }
       
    @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;
    }
}
       
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("downloader异常");
        } finally {
        }
    }
}
       
public class Application {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        MyCallable t1 = new MyCallable("https://ss0.bdstatic.com/70cFuHSh_Q1YnxGkpoWK1HF6hhy/it/u=3246675119,2528014287&fm=26&gp=0.jpg", "csgo1.jpg");
        MyCallable t2 = new MyCallable("https://ss0.bdstatic.com/70cFuHSh_Q1YnxGkpoWK1HF6hhy/it/u=3246675119,2528014287&fm=26&gp=0.jpg", "csgo2.jpg");
        MyCallable t3 = new MyCallable("https://ss0.bdstatic.com/70cFuHSh_Q1YnxGkpoWK1HF6hhy/it/u=3246675119,2528014287&fm=26&gp=0.jpg", "csgo3.jpg");
       
        // 创建执行服务
        ExecutorService ser = Executors.newFixedThreadPool(3);
       
        // 提交执行
        Future<Boolean> r1 = ser.submit(t1);
        Future<Boolean> r2 = ser.submit(t2);
        Future<Boolean> r3 = ser.submit(t3);
       
        // 获取结果
        boolean rs1 = r1.get();
        boolean rs2 = r2.get();
        boolean rs3 = r3.get();
       
        // 关闭服务
        ser.shutdown();
    }
}
java, concurrent programming
Java Concurrent Programming Thread
本文由作者按照 CC BY 4.0 进行授权