waitnotifydemo.java

《J2ME图形应用基础》第二章

/*
 * WaitNotifyDemo.java
 *
 * Created on 2005年4月11日, 下午4:38
 */

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

/**
 *
 * @author  Liu Bin
 * @version
 */
public class WaitNotifyDemo extends MIDlet implements CommandListener {
    //Display管理
    Display display = null;
    Form form = new Form("等待和唤醒演示");
    
    Command cmdExit = new Command("退出", Command.STOP, 1);
    Command cmdRun = new Command("运行", Command.ITEM, 2);
    Command cmdStop = new Command("停止", Command.ITEM, 2);
    
    //共享变量
    private int contents = 0;
    private boolean available = false;
    
    MyThreaad p1, p2;
    
    public WaitNotifyDemo() {
        form.addCommand(cmdExit);
        form.addCommand(cmdRun);
        form.setCommandListener(this);
    }
    public void startApp() {
        
        display = Display.getDisplay(this); //获得当前MIDlet的Display对象
        display.setCurrent(form);           //设置form对象为当前显示对象
    }
    
    public void pauseApp() {
    }
    
    public void destroyApp(boolean unconditional) {
        notifyDestroyed();
    }
    
    /**
     * 处理命令按钮事件
     */
    public void commandAction(Command cmd, Displayable d) {
        if (cmd == cmdExit) {
            destroyApp(true);
        } else if (cmd == cmdRun) {
            //创建线程1
            p1 = new MyThreaad(1, false);
            //执行线程1
            p1.start();
            
            //创建线程2
            p2 = new MyThreaad(2, true);
            //执行线程2
            p2.start();
            
            form.removeCommand(cmdRun);
            form.addCommand(cmdStop);
        } else if (cmd == cmdStop) {
            form.removeCommand(cmdStop);
            form.addCommand(cmdRun);
            
            p1.stopFlag = true;
            p2.stopFlag = true;
        }
    }
    
    public synchronized int get() {
        while (available == false) {
            try {
                wait();
            } catch (InterruptedException e) {
                System.out.println("Gut Exception: " + e.toString());
            }
        }
        available = false;
        notifyAll();
        return contents;
    }
    
    public synchronized void put(int value) {
        while (available == true) {
            try {
                wait();
            } catch (InterruptedException e) {
                System.out.println("Put Exception: " + e.toString());
            }
        }
        contents = value;
        available = true;
        notifyAll();
    }
    
    
    /**
     * 从Thread继承创建线程
     */
    class MyThreaad extends Thread {
        //当前线程的ID标识
        long id;
        boolean isRead;
        public boolean stopFlag;
        
        MyThreaad(long id, boolean isRead) {
            this.isRead = isRead;
            this.id = id;
        }
        
        public void run() {
            stopFlag = false;
            System.out.println("线程"+ id + "开始执行\n");
            int i=0;
            while (!stopFlag) {
                if (isRead) {
                    put(++i);
                    System.out.println("线程"+id + "，设置值为：" + i);   
                } else {
                    System.out.println("线程"+id + "，读取值为：" + get());
                }
            }
            System.out.println("线程"+ id + "执行完毕\n");
        }
    }
}