void setDaemon(boolean daemon)
描述 (Description)
java.lang.ThreadGroup.setDaemon()方法更改此线程组的守护程序状态。 守护程序线程组在其最后一个线程停止或其最后一个线程组被销毁时会自动销毁。
声明 (Declaration)
以下是java.lang.ThreadGroup.setDaemon()方法的声明
public final void setDaemon(boolean daemon)
参数 (Parameters)
daemon - 如果为true，则将此线程组标记为守护程序线程组; 否则，将此线程组标记为正常。
返回值 (Return Value)
此方法不返回任何值。
异常 (Exception)
SecurityException - 如果当前线程无法修改此线程组。
例子 (Example)
以下示例显示了java.lang.ThreadGroup.setDaemon（）方法的用法。
package com.iowiki;
import java.lang.*;
public class ThreadGroupDemo implements Runnable {
public static void main(String[] args) {
ThreadGroupDemo tg = new ThreadGroupDemo();
tg.func();
}
public void func() {
try {
// create a parent ThreadGroup
ThreadGroup pGroup = new ThreadGroup("Parent ThreadGroup");
// daemon status is set to true
pGroup.setDaemon(true);
// create a child ThreadGroup for parent ThreadGroup
ThreadGroup cGroup = new ThreadGroup(pGroup, "Child ThreadGroup");
// daemon status is set to true
cGroup.setDaemon(true);
// create a thread
Thread t1 = new Thread(pGroup, this);
System.out.println("Starting " + t1.getName() + "...");
t1.start();
// create another thread
Thread t2 = new Thread(cGroup, this);
System.out.println("Starting " + t2.getName() + "...");
t2.start();
// returns true if this thread group is a daemon thread group
System.out.println("Is " + pGroup.getName() + " a daemon
ThreadGroup? " + pGroup.isDaemon());
System.out.println("Is " + cGroup.getName() + " a daemon
ThreadGroup? " + cGroup.isDaemon());
// block until the other threads finish
t1.join();
t2.join();
} catch (InterruptedException ex) {
System.out.println(ex.toString());
}
}
// implements run()
public void run() {
for(int i = 0;i < 1000;i++) {
i++;
}
System.out.println(Thread.currentThread().getName() +
" finished executing.");
}
}
让我们编译并运行上面的程序，这将产生以下结果 -
Starting Thread-0...
Starting Thread-1...
Is Parent ThreadGroup a daemonThreadGroup? true
Is Child ThreadGroup a daemonThreadGroup? true
Thread-0 finished executing.
Thread-1 finished executing.
