ThreadGroup解讀
ThreadGroup 可以把thread的名字統一起來。一起處理catch。
ThreadGroup是Java提供的一種對線程進行分組管理的手段，可以對所有線程以組爲單位進行操作，如設置優先級、守護線程等。
線程組也有父子的概念，如下圖：
線程組的基本操作
1.1 線程組的創建
public class ThreadGroupCreator {
public static void main(String[] args) {
//獲取當前線程的group
ThreadGroup currentGroup = Thread.currentThread().getThreadGroup();
//在當前線程執行流中新建一個Group1
ThreadGroup group1 = new ThreadGroup("Group1");
//Group1的父線程,就是main線程所在Group
System.out.println(group1.getParent() == currentGroup);
//定義Group2, 指定group1爲其父線程
ThreadGroup group2 = new ThreadGroup(group1, "Group2");
System.out.println(group2.getParent() == group1);
}
}
ThreadGroup是位於java.lang包下的一個類,用於統一的線程管理.一旦一個線程加入到一個線程組後,就不能更換線程所在的線程組
1.2 複製線程組中活躍的線程信息
Thread[] threads = new Thread[num];
threadGroup.enumerate(threads);
for (Thread t : threads) {
System.out.println("線程名-" + t.getName());
}
1.3 線程組的基本操作
public class ThreadGroupBasic {
public static void main(String[] args) throws InterruptedException {
ThreadGroup group = new ThreadGroup("group1");
Thread thread = new Thread(group, () -> {
while(true) {
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}, "thread");
thread.setDaemon(true);
thread.start();
TimeUnit.MILLISECONDS.sleep(1);
ThreadGroup mainGroup = Thread.currentThread().getThreadGroup();
//遞歸獲取mainGroup中活躍線程的估計值
System.out.println("activeCount = " + mainGroup.activeCount());
//遞歸獲mainGroup中的活躍子group
System.out.println("activeGroupCount = " + mainGroup.activeGroupCount());
//獲取group的優先級, 默認爲10
System.out.println("getMaxPriority = " + mainGroup.getMaxPriority());
//獲取group的名字
System.out.println("getName = " + mainGroup.getName());
//獲取group的父group, 如不存在則返回null
System.out.println("getParent = " + mainGroup.getParent());
//活躍線程信息全部輸出到控制檯
mainGroup.list();
System.out.println("----------------------------");
//判斷當前group是不是給定group的父線程, 如果兩者一樣,也會返回true
System.out.println("parentOf = " + mainGroup.parentOf(group));
System.out.println("parentOf = " + mainGroup.parentOf(mainGroup));
}
}
線程組的其他操作
2.1 線程組的Interrupt
public class ThreadGroupInterrupt {
public static void main(String[] args) throws InterruptedException {
ThreadGroup group = new ThreadGroup("TestGroup");
new Thread(group, () -> {
while(true) {
try {
TimeUnit.MILLISECONDS.sleep(2);
} catch (InterruptedException e) {
//received interrupt signal and clear quickly
System.out.println(Thread.currentThread().isInterrupted());
break;
}
}
System.out.println("t1 will exit");
}, "t1").start();
new Thread(group, () -> {
while(true) {
try {
TimeUnit.MILLISECONDS.sleep(2);
} catch (InterruptedException e) {
//received interrupt signal and clear quickly
System.out.println(Thread.currentThread().isInterrupted());
break;
}
}
System.out.println("t2 will exit");
}, "t2").start();
//make sure all threads start
TimeUnit.MILLISECONDS.sleep(2);
group.interrupt();
}
}
2.2 線程組的destroy
public class ThreadGroupDestroy {
public static void main(String[] args) {
ThreadGroup group = new ThreadGroup("TestGroup");
ThreadGroup mainGroup = Thread.currentThread().getThreadGroup();
//before destroy
System.out.println("group.isDestroyed=" + group.isDestroyed());
mainGroup.list();
group.destroy();
//after destroy
System.out.println("group.isDestroyed=" + group.isDestroyed());
mainGroup.list();
}
}
2.3 線程組設置守護線程組
線程組設置爲守護線程組，並不會影響其線程是否爲守護線程，僅僅表示當它內部沒有active的線程的時候，會自動destroy。
public class ThreadGroupDaemon {
public static void main(String[] args) throws InterruptedException {
ThreadGroup group1 = new ThreadGroup("group1");
new Thread(group1, () -> {
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}, "group1-thread1").start();
ThreadGroup group2 = new ThreadGroup("group2");
new Thread(group2, () -> {
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}, "group1-thread2").start();
group2.setDaemon(true);
TimeUnit.SECONDS.sleep(3);
System.out.println(group1.isDestroyed());
System.out.println(group2.isDestroyed());
}
}