使用Runable接口和Thread类实现线程的异同

相同之处

• 在实现Runable接口的类和继承Thread的类中均需要重写run()方法
• 在启动线程时均通过调用start()方法来执行run()方法中的语句

不同之处

• Runable是接口、Thread是类，使用时语法不同

  // 实现Runable接口
  public class MyThreadByRunable implements Runable {
      @Override
      public void run() {
          ...
      }
  }
  
  // 继承Thread类
  public class MyThreadByThread extends Thread {
      private String name;
      
      public MyThread(String name) {
          this.name = name;
      }
      
      @Override
      public void run() {
          ...
      }
  }
  
  // --------------------------------------------------------------
  public class Main {
      public static void main(String[] args) {
          Runable myThread1 = new MyThreadByRunable();
          new Thread(myThread1, "my_thread_impl_Runable").start();
          
          MyThreadByThread myThread2 = new MyThreadByThread("my_thread_extends_Thread");
          myThread2.start();        
      }
  }
  

• 由于java单继承的特性，使用Runable接口使自定义的线程类具有更好的拓展性，而继承Thread类的自定义线程类无法实现其他的继承

• 使用Runable接口易于实现资源共享，而继承Thread类不易于实现资源共享

  示例1：使用Runable接口

  public class MyThreadByRunable implements Runnable {
      private int count = 7;
  
      @Override
      public void run() {
          for (int i = 0; i < 3; i++) {
              System.out.println(Thread.currentThread().getName() + "is running, count = " + count--);
              try {
                  Thread.sleep((int) (Math.random() * 10));
              } catch (InterruptedException e) {
                  e.printStackTrace();
              }
          }
      }
  }
  
  public class Main {
  
      public static void main(String[] args) {
          Runnable myThread1 = new MyThreadByRunable();
          new Thread(myThread1, "Thread_1").start();
          new Thread(myThread1, "Thread_2").start();
          new Thread(myThread1, "Thread_3").start();
      }
  }
  

  !
  image

  可以看到三个线程共享了count值，因为它们是从同一个实例myThread1开启的

示例2：使用Thread类

public class MyThreadByThread extends Thread {
    private String name;

    public int count = 7;

    public MyThreadByThread(String name) {
        this.name = name;
    }

    @Override
    public void run() {
        for (int i = 0; i < 3; i++) {
            System.out.println(this.name + " is running, count = " + count--);
            try {
                Thread.sleep((int) (Math.random() * 10));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

public class Main {

    public static void main(String[] args) {
        MyThreadByThread myThread4 = new MyThreadByThread("Thread_4");
        // 如果用同一个线程对象开启多个线程会报异常
        myThread4.start();
        myThread4.start();
    }
}

image

// 使用Thread类来开启多个线程的正确写法
public class Main {

    public static void main(String[] args) {
        MyThreadByThread myThread4 = new MyThreadByThread("Thread_4");
        MyThreadByThread myThread5 = new MyThreadByThread("Thread_5");
        MyThreadByThread myThread6 = new MyThreadByThread("Thread_6");
        myThread4.start();
        myThread5.start();
        myThread6.start();

    }
}

image

可以看到三个线程并没有共享资源，因为它们必须由不同线程对象开启。

参考

• 多线程——继承Thread 类和实现Runnable 接口的区别