线程的优先级[Java编程]

//: Counter5.java
// Adjusting the priorities of threads
import java.awt.*;
import java.awt.event.*;
import java.applet.*;

class Ticker2 extends Thread {
  private Button 
    b = new Button("Toggle"),
    incPriority = new Button("up"),
    decPriority = new Button("down");
  private TextField 
    t = new TextField(10),
    pr = new TextField(3); // Display priority
  private int count = 0;
  private boolean runFlag = true;
  public Ticker2(Container c) {
    b.addActionListener(new ToggleL());
    incPriority.addActionListener(new UpL());
    decPriority.addActionListener(new DownL());
    Panel p = new Panel();
    p.add(t);
    p.add(pr);
    p.add(b);
    p.add(incPriority);
    p.add(decPriority);
    c.add(p);
  }
  class ToggleL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      runFlag = !runFlag;
    }
  }
  class UpL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      int newPriority = getPriority() + 1;
      if(newPriority > Thread.MAX_PRIORITY)
        newPriority = Thread.MAX_PRIORITY;
      setPriority(newPriority);
    }
  }
  class DownL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      int newPriority = getPriority() - 1;
      if(newPriority < Thread.MIN_PRIORITY)
        newPriority = Thread.MIN_PRIORITY;
      setPriority(newPriority);
    }
  }
  public void run() {
    while (true) {
      if(runFlag) {
        t.setText(Integer.toString(count++));
        pr.setText(
          Integer.toString(getPriority()));
      }
      yield();
    }
  }
}

public class Counter5 extends Applet {
  private Button 
    start = new Button("Start"),
    upMax = new Button("Inc Max Priority"),
    downMax = new Button("Dec Max Priority");
  private boolean started = false;
  private static final int SIZE = 10;
  private Ticker2[] s = new Ticker2[SIZE];
  private TextField mp = new TextField(3);
  public void init() {
    for(int i = 0; i < s.length; i++)
      s[i] = new Ticker2(this);
    add(new Label("MAX_PRIORITY = "
      + Thread.MAX_PRIORITY));
    add(new Label("MIN_PRIORITY = "
      + Thread.MIN_PRIORITY));
    add(new Label("Group Max Priority = "));
    add(mp); 
    add(start);
    add(upMax); add(downMax);
    start.addActionListener(new StartL());
    upMax.addActionListener(new UpMaxL());
    downMax.addActionListener(new DownMaxL());
    showMaxPriority();
    // Recursively display parent thread groups:
    ThreadGroup parent = 
      s[0].getThreadGroup().getParent();
    while(parent != null) {
      add(new Label(
        "Parent threadgroup max priority = "
        + parent.getMaxPriority()));
      parent = parent.getParent();
    }
  }
  public void showMaxPriority() {
    mp.setText(Integer.toString(
      s[0].getThreadGroup().getMaxPriority()));
  }
  class StartL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      if(!started) {
        started = true;
        for(int i = 0; i < s.length; i++)
          s[i].start();
      }
    }
  }
  class UpMaxL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      int maxp = 
        s[0].getThreadGroup().getMaxPriority();
      if(++maxp > Thread.MAX_PRIORITY)
        maxp = Thread.MAX_PRIORITY;
      s[0].getThreadGroup().setMaxPriority(maxp);
      showMaxPriority();
    }
  }
  class DownMaxL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      int maxp = 
        s[0].getThreadGroup().getMaxPriority();
      if(--maxp < Thread.MIN_PRIORITY)
        maxp = Thread.MIN_PRIORITY;
      s[0].getThreadGroup().setMaxPriority(maxp);
      showMaxPriority();
    }
  }
  public static void main(String[] args) {
    Counter5 applet = new Counter5();
    Frame aFrame = new Frame("Counter5");
    aFrame.addWindowListener(
      new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
          System.exit(0);
        }
      });
    aFrame.add(applet, BorderLayout.CENTER);
    aFrame.setSize(300, 600);
    applet.init();
    applet.start();
    aFrame.setVisible(true);
  }
} ///:~