Java基礎之線程——使用Runnable接口（JumbleNames)

控制臺程序。

除了定義Thread新的子類外，還可以在類中實現Runnable接口。您會發現這比從Thread類派生子類更方便，因為在實現Runnable接口時可以從不是Thread的類派生子類，并且仍然表示線程。Java只允許有單個基類，如果類派生于Thread，就不能再繼承其他類中的功能。Runnabel接口只定義了方法run()，這個方法在啟動線程時執行。

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
}

不能在這個構造函數中調用setDaemon()方法，因為這個類并非派生于Thread類。
在創建表示線程的對象之后并且在調用run()方法之前，需要調用setDaemon()方法。

在main()方法中，仍然為每個執行線程創建了Thread對象，但這次使用的構造函數把Runnable類型的對象作為參數。

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