我正在参加「掘金·启航计划」
看代码的时候，偶然发现了一个东西ThreadGroup，也很丢人，一直没有看到过这个，这里就写个笔记记录下
先看注释
/**
* A thread group represents a set of threads. In addition, a thread
* group can also include other thread groups. The thread groups form
* a tree in which every thread group except the initial thread group
* has a parent.
一个线程组代表一堆线程，此外，一个线程组可以包括其他线程组。线程组形成了一棵树，其中除了初始线程组之外的每个线程组都有一个父级。
* <p>
* A thread is allowed to access information about its own thread
* group, but not to access information about its thread group's
* parent thread group or any other thread groups.
*
一个线程允许访问有关自己线程组的信息，但不能访问它的线程组的父线程组或任何其他线程组的信息
* @author unascribed
* @since JDK1.0
*/
public static void main(String[] args) throws InterruptedException {
Object key=new Object();
ThreadGroup parentThreadGroup=new ThreadGroup("parent");
ThreadGroup sonThreadGroup=new ThreadGroup(parentThreadGroup,"son");
new Thread(parentThreadGroup,()->{
synchronized (key){
try {
System.out.println("------------");
System.out.println("parent start.....");
Thread.sleep(3000);
System.out.println("parent over.....");
System.out.println(Thread.currentThread().getThreadGroup().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getParent().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getParent().getParent().getName());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
new Thread(sonThreadGroup,()->{
synchronized (key){
try {
System.out.println("------------");
System.out.println("son start ......");
Thread.sleep(3000);
System.out.println("son over ......");
System.out.println(Thread.currentThread().getThreadGroup().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getParent().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getParent().getParent().getName());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
new Thread(()->{
synchronized (key){
try {
System.out.println("------------");
System.out.println("other start ......");
Thread.sleep(3000);
System.out.println("other over ......");
System.out.println(Thread.currentThread().getThreadGroup().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getParent().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getParent().getParent().getName());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
Thread.sleep(1000);
try{
//销毁此线程组及其所有子组。此线程组必须为空，表示该线程组中的所有线程都已停止。
// parentThreadGroup.destroy();
// System.out.println("isDestory?:"+parentThreadGroup.isDestroyed());
//停止此线程组中的所有线程。（废弃）
// parentThreadGroup.stop();
//中断此线程组中的所有线程。
// parentThreadGroup.interrupt();
System.out.println( parentThreadGroup.activeCount());
}catch (Exception e){
System.out.println("isDestory?:"+parentThreadGroup.isDestroyed());
}
new Thread(sonThreadGroup,()->{
synchronized (key){
try {
System.out.println("------------");
System.out.println("later start ......");
Thread.sleep(3000);
System.out.println("later over ......");
System.out.println(Thread.currentThread().getThreadGroup().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getParent().getName());
System.out.println(Thread.currentThread().getThreadGroup().getParent().getParent().getParent().getName());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
}
结果
------------
parent start.....
2
parent over.....
parent
main
system
------------
later start ......
Exception in thread "Thread-0" java.lang.NullPointerException
at com.mountain.monk.netty1.ThreadGroupDemo.lambda$main$0(ThreadGroupDemo.java:21)
at java.lang.Thread.run(Thread.java:748)
later over ......
son
parent
main
system
------------
other start ......
other over ......
main
system
------------
son start ......
Exception in thread "Thread-2" java.lang.NullPointerException
at com.mountain.monk.netty1.ThreadGroupDemo.lambda$main$2(ThreadGroupDemo.java:59)
at java.lang.Thread.run(Thread.java:748)
son over ......
son
parent
main
system
大致总结
总的来说没啥用，可能方便管理？
线程创建都要指定一个，没有就指定为SecurityManager的线程组，并不影响锁
- interrupt：中断当前线程组中的线程，极其子线程
- destroy：销毁，但是感觉没啥用
