多线程编程<四>

/**
 * 守护线程daemon['diːmən]
 * @author Administrator
 *
 */
public class DaemonDemo {
    public static void main(String[] args) {
        MyDaemon dt = new MyDaemon();
        
        if (dt.thrd.isDaemon()) {
            System.out.println("dt is a daemon thread.");
        }
        System.out.println("Sleeping in main thread.");
        try{
            Thread.sleep(10000);
        }
        catch(InterruptedException exc){
            System.out.println("Main thread interrupted.");
        }
        
        System.out.println("\nMain thread ending.");
    }
}

class MyDaemon implements Runnable{
    Thread thrd;
    
    public MyDaemon() {
        thrd = new Thread(this);
        thrd.setDaemon(true);//守护线程：当用户线程结束时，守护线程也结束。
        thrd.start();
    }

    @Override
    public void run() {
        
        try {
            for(;;) {
                System.out.print(".");
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            System.out.println("MyDaemon interrupted.");
        }
    }
}

一个简单的Reminder

import java.util.Calendar;
import java.util.GregorianCalendar;


public class ReminderDemo {
    public static void main(String[] args) {
        Reminder mt = new Reminder("Call Harry", 2);
        
        Reminder mt2 = new Reminder("Meet with Bill", new GregorianCalendar(2014,4,14,21,14));
        
        for(int i = 0; i < 20; i++){
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                System.out.println("Main thread interrupted.");
            }
            System.out.print(".");
        }
        System.out.println("\nMain thread ending.");
    }
}
class Reminder implements Runnable {
    
    Calendar reminderTime;
    
    String message;
    
    public Reminder(String msg, int delay) {
        message = msg;
        reminderTime = Calendar.getInstance();
        reminderTime.add(Calendar.SECOND, delay);
        System.out.printf("Reminder set for %tD %1$tr\n", reminderTime);
        Thread dThrd = new Thread(this);
        dThrd.setDaemon(true);
        dThrd.start();
    }
    
    public Reminder(String msg, Calendar cal) {
        message = msg;
        
        reminderTime = cal;
        System.out.printf("Reminder set for %tD %1$tr\n", reminderTime);//变元索引
        Thread dThrd = new Thread(this);
        dThrd.setDaemon(true);
        dThrd.start();
    }
    @Override
    public void run() {
        try {
            for(;;){
                Calendar curTime = Calendar.getInstance();
                if(curTime.compareTo(reminderTime) >= 0) {
                    System.out.println("\n" + message + "\n");
                    break;
                }
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            System.out.println("Reminder interrupted.");
        }
    }
    
}