package com.itsoku.chat02;	
import java.util.concurrent.TimeUnit;	
/**	
 * &lt;b&gt;description&lt;/b&gt;：&lt;br&gt;	
 * &lt;b&gt;time&lt;/b&gt;：2019/7/13 17:53 &lt;br&gt;	
 * &lt;b&gt;author&lt;/b&gt;：微信公眾號：路人甲Java，專注于java技術(shù)分享（帶你玩轉(zhuǎn) 爬蟲、分布式事務(wù)、異步消息服務(wù)、任務(wù)調(diào)度、分庫分表、大數(shù)據(jù)等），喜歡請關(guān)注！	
 */	
public class Demo1 {	
    public static class R1 implements Runnable {	
        @Override	
        public void run() {	
            System.out.println("threadName:" + Thread.currentThread().getName());	
            try {	
                TimeUnit.SECONDS.sleep(3);	
            } catch (InterruptedException e) {	
                e.printStackTrace();	
            }	
        }	
    }	
    public static void main(String[] args) throws InterruptedException {	
        ThreadGroup threadGroup = new ThreadGroup("thread-group-1");	
        Thread t1 = new Thread(threadGroup, new R1(), "t1");	
        Thread t2 = new Thread(threadGroup, new R1(), "t2");	
        t1.start();	
        t2.start();	
        TimeUnit.SECONDS.sleep(1);	
        System.out.println("活動線程數(shù):" + threadGroup.activeCount());	
        System.out.println("活動線程組:" + threadGroup.activeGroupCount());	
        System.out.println("線程組名稱:" + threadGroup.getName());	
    }	
}

輸出結(jié)果：

threadName:t1
threadName:t2
活動線程數(shù):2
活動線程組:0
線程組名稱:thread-group-1

activeCount()方法可以返回線程組中的所有活動線程數(shù)，包含下面的所有子孫節(jié)點的線程，由于線程組中的線程是動態(tài)變化的，這個值只能是一個估算值。

為線程組指定父線程組

創(chuàng)建線程組的時候，可以給其指定一個父線程組，也可以不指定，如果不指定父線程組，則父線程組為當(dāng)前線程的線程組，java api有2個常用的構(gòu)造方法用來創(chuàng)建線程組：

public ThreadGroup(String name) 	
public ThreadGroup(ThreadGroup parent, String name)

第一個構(gòu)造方法未指定父線程組，看一下內(nèi)部的實現(xiàn)：

public ThreadGroup(String name) {	
        this(Thread.currentThread().getThreadGroup(), name);	
    }

系統(tǒng)自動獲取當(dāng)前線程的線程組作為默認父線程組。

上一段示例代碼：

package com.itsoku.chat02;	
import java.util.concurrent.TimeUnit;	
/**	
 * &lt;b&gt;description&lt;/b&gt;：&lt;br&gt;	
 * &lt;b&gt;time&lt;/b&gt;：2019/7/13 17:53 &lt;br&gt;	
 * &lt;b&gt;author&lt;/b&gt;：微信公眾號：路人甲Java，專注于java技術(shù)分享（帶你玩轉(zhuǎn) 爬蟲、分布式事務(wù)、異步消息服務(wù)、任務(wù)調(diào)度、分庫分表、大數(shù)據(jù)等），喜歡請關(guān)注！	
 */	
public class Demo2 {	
    public static class R1 implements Runnable {	
        @Override	
        public void run() {	
            Thread thread = Thread.currentThread();	
            System.out.println("所屬線程組:" + thread.getThreadGroup().getName() + ",線程名稱:" + thread.getName());	
            try {	
                TimeUnit.SECONDS.sleep(3);	
            } catch (InterruptedException e) {	
                e.printStackTrace();	
            }	
        }	
    }	
    public static void main(String[] args) throws InterruptedException {	
        ThreadGroup threadGroup1 = new ThreadGroup("thread-group-1");	
        Thread t1 = new Thread(threadGroup1, new R1(), "t1");	
        Thread t2 = new Thread(threadGroup1, new R1(), "t2");	
        t1.start();	
        t2.start();	
        TimeUnit.SECONDS.sleep(1);	
        System.out.println("threadGroup1活動線程數(shù):" + threadGroup1.activeCount());	
        System.out.println("threadGroup1活動線程組:" + threadGroup1.activeGroupCount());	
        System.out.println("threadGroup1線程組名稱:" + threadGroup1.getName());	
        System.out.println("threadGroup1父線程組名稱:" + threadGroup1.getParent().getName());	
        System.out.println("----------------------");	
        ThreadGroup threadGroup2 = new ThreadGroup(threadGroup1, "thread-group-2");	
        Thread t3 = new Thread(threadGroup2, new R1(), "t3");	
        Thread t4 = new Thread(threadGroup2, new R1(), "t4");	
        t3.start();	
        t4.start();	
        TimeUnit.SECONDS.sleep(1);	
        System.out.println("threadGroup2活動線程數(shù):" + threadGroup2.activeCount());	
        System.out.println("threadGroup2活動線程組:" + threadGroup2.activeGroupCount());	
        System.out.println("threadGroup2線程組名稱:" + threadGroup2.getName());	
        System.out.println("threadGroup2父線程組名稱:" + threadGroup2.getParent().getName());	
        System.out.println("----------------------");	
        System.out.println("threadGroup1活動線程數(shù):" + threadGroup1.activeCount());	
        System.out.println("threadGroup1活動線程組:" + threadGroup1.activeGroupCount());	
        System.out.println("----------------------");	
        threadGroup1.list();	
    }	
}

輸出結(jié)果：

所屬線程組:thread-group-1,線程名稱:t1
所屬線程組:thread-group-1,線程名稱:t2
threadGroup1活動線程數(shù):2
threadGroup1活動線程組:0
threadGroup1線程組名稱:thread-group-1
threadGroup1父線程組名稱:main
----------------------
所屬線程組:thread-group-2,線程名稱:t4
所屬線程組:thread-group-2,線程名稱:t3
threadGroup2活動線程數(shù):2
threadGroup2活動線程組:0
threadGroup2線程組名稱:thread-group-2
threadGroup2父線程組名稱:thread-group-1
----------------------
threadGroup1活動線程數(shù):4
threadGroup1活動線程組:1
----------------------
java.lang.ThreadGroup[name=thread-group-1,maxpri=10]
Thread[t1,5,thread-group-1]
Thread[t2,5,thread-group-1]
java.lang.ThreadGroup[name=thread-group-2,maxpri=10]
Thread[t3,5,thread-group-2]
Thread[t4,5,thread-group-2]

代碼解釋：

1.threadGroup1未指定父線程組，系統(tǒng)獲取了主線程的線程組作為threadGroup1的父線程組，輸出結(jié)果中是：main

2.threadGroup1為threadGroup2的父線程組

3.threadGroup1活動線程數(shù)為4，包含了threadGroup1線程組中的t1、t2，以及子線程組threadGroup2中的t3、t4

4.線程組的list()方法，將線程組中的所有子孫節(jié)點信息輸出到控制臺，用于調(diào)試使用

根線程組

獲取根線程組

package com.itsoku.chat02;	
/**	
 * &lt;b&gt;description&lt;/b&gt;：&lt;br&gt;	
 * &lt;b&gt;time&lt;/b&gt;：2019/7/13 17:53 &lt;br&gt;	
 * &lt;b&gt;author&lt;/b&gt;：微信公眾號：路人甲Java，專注于java技術(shù)分享（帶你玩轉(zhuǎn) 爬蟲、分布式事務(wù)、異步消息服務(wù)、任務(wù)調(diào)度、分庫分表、大數(shù)據(jù)等），喜歡請關(guān)注！	
 */	
public class Demo3 {	
    public static void main(String[] args) {	
        System.out.println(Thread.currentThread());	
        System.out.println(Thread.currentThread().getThreadGroup());	
        System.out.println(Thread.currentThread().getThreadGroup().getParent());	
        System.out.println(Thread.currentThread().getThreadGroup().getParent().getParent());	
    }	
}

運行上面代碼，輸出：

Thread[main,5,main]
java.lang.ThreadGroup[name=main,maxpri=10]
java.lang.ThreadGroup[name=system,maxpri=10]
null

從上面代碼可以看出：

1.主線程的線程組為main

2.根線程組為system

看一下ThreadGroup的源碼：

private ThreadGroup() {     // called from C code	
        this.name = "system";	
        this.maxPriority = Thread.MAX_PRIORITY;	
        this.parent = null;	
    }

發(fā)現(xiàn)ThreadGroup默認構(gòu)造方法是private的，是由c調(diào)用的，創(chuàng)建的正是system線程組。

批量停止線程

調(diào)用線程組interrupt()，會將線程組樹下的所有子孫線程中斷標(biāo)志置為true，可以用來批量中斷線程。

示例代碼：

package com.itsoku.chat02;	
import java.util.concurrent.TimeUnit;	
/**	
 * &lt;b&gt;description&lt;/b&gt;：&lt;br&gt;	
 * &lt;b&gt;time&lt;/b&gt;：2019/7/13 17:53 &lt;br&gt;	
 * &lt;b&gt;author&lt;/b&gt;：微信公眾號：路人甲Java，專注于java技術(shù)分享（帶你玩轉(zhuǎn) 爬蟲、分布式事務(wù)、異步消息服務(wù)、任務(wù)調(diào)度、分庫分表、大數(shù)據(jù)等），喜歡請關(guān)注！	
 */	
public class Demo4 {	
    public static class R1 implements Runnable {	
        @Override	
        public void run() {	
            Thread thread = Thread.currentThread();	
            System.out.println("所屬線程組:" + thread.getThreadGroup().getName() + ",線程名稱:" + thread.getName());	
            while (!thread.isInterrupted()) {	
                ;	
            }	
            System.out.println("線程:" + thread.getName() + "停止了！");	
        }	
    }	
    public static void main(String[] args) throws InterruptedException {	
        ThreadGroup threadGroup1 = new ThreadGroup("thread-group-1");	
        Thread t1 = new Thread(threadGroup1, new R1(), "t1");	
        Thread t2 = new Thread(threadGroup1, new R1(), "t2");	
        t1.start();	
        t2.start();	
        ThreadGroup threadGroup2 = new ThreadGroup(threadGroup1, "thread-group-2");	
        Thread t3 = new Thread(threadGroup2, new R1(), "t3");	
        Thread t4 = new Thread(threadGroup2, new R1(), "t4");	
        t3.start();	
        t4.start();	
        TimeUnit.SECONDS.sleep(1);	
        System.out.println("-----------threadGroup1信息-----------");	
        threadGroup1.list();	
        System.out.println("----------------------");	
        System.out.println("停止線程組：" + threadGroup1.getName() + "中的所有子孫線程");	
        threadGroup1.interrupt();	
        TimeUnit.SECONDS.sleep(2);	
        System.out.println("----------threadGroup1停止后，輸出信息------------");	
        threadGroup1.list();	
    }	
}

輸出：

所屬線程組:thread-group-1,線程名稱:t1
所屬線程組:thread-group-1,線程名稱:t2
所屬線程組:thread-group-2,線程名稱:t3
所屬線程組:thread-group-2,線程名稱:t4
-----------threadGroup1信息-----------
java.lang.ThreadGroup[name=thread-group-1,maxpri=10]
Thread[t1,5,thread-group-1]
Thread[t2,5,thread-group-1]
java.lang.ThreadGroup[name=thread-group-2,maxpri=10]
Thread[t3,5,thread-group-2]
Thread[t4,5,thread-group-2]
----------------------
停止線程組：thread-group-1中的所有子孫線程
線程:t4停止了！
線程:t2停止了！
線程:t1停止了！
線程:t3停止了！
----------threadGroup1停止后，輸出信息------------
java.lang.ThreadGroup[name=thread-group-1,maxpri=10]
java.lang.ThreadGroup[name=thread-group-2,maxpri=10]