Java基础之线程——使用Runnable接口（JumbleNames)

控制台程序。

除了定义Thread新的子类外，还可以在类中实现Runnable接口。您会发现这比从Thread类派生子类更方便，因为在实现Runnable接口时可以从不是Thread的类派生子类，并且仍然表示线程。Java只允许有单个基类，如果类派生于Thread，就不能再继承其他类中的功能。Runnabel接口只定义了方法run()，这个方法在启动线程时执行。

import java.io.IOException;

public class JumbleNames implements Runnable {
  // Constructor
  public JumbleNames(String firstName, String secondName, long delay) {
    this.firstName = firstName;                                        // Store the first name
    this.secondName = secondName;                                      // Store the second name
    aWhile = delay;                                                    // Store the delay
  }

  // Method where thread execution will start
  public void run() {
    try {
      while(true) {                                                    // Loop indefinitely...
        System.out.print(firstName);                                   // Output first name
        Thread.sleep(aWhile);                                          // Wait aWhile msec.
        System.out.print(secondName+"\n");                             // Output second name
      }
    } catch(InterruptedException e) {                                  // Handle thread interruption
      System.out.println(firstName + secondName + e);                  // Output the exception
    }
  }

  public static void main(String[] args) {
    // Create three threads
    Thread first = new Thread(new JumbleNames("Hopalong ", "Cassidy ", 200L));
    Thread second = new Thread(new JumbleNames("Marilyn ", "Monroe ", 300L));
    Thread third = new Thread(new JumbleNames("Slim ", "Pickens ", 500L));

    // Set threads as daemon
    first.setDaemon(true);
    second.setDaemon(true);
    third.setDaemon(true);
    System.out.println("Press Enter when you have had enough...\n");
    first.start();                                                     // Start the first thread
    second.start();                                                    // Start the second thread
    third.start();                                                     // Start the third thread
    try {
      System.in.read();                                                // Wait until Enter key pressed
      System.out.println("Enter pressed...\n");

    } catch (IOException e) {                                          // Handle IO exception
      System.err.println(e);                                           // Output the exception
    }
    System.out.println("Ending main()");
    return;
  }

  private String firstName;                                            // Store for first name
  private String secondName;                                           // Store for second name
  private long aWhile;                                                 // Delay in milliseconds
}

不能在这个构造函数中调用setDaemon()方法，因为这个类并非派生于Thread类。
在创建表示线程的对象之后并且在调用run()方法之前，需要调用setDaemon()方法。

在main()方法中，仍然为每个执行线程创建了Thread对象，但这次使用的构造函数把Runnable类型的对象作为参数。