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This article mainly introduces the relevant knowledge of "how to use thread groups in Java". Xiaobian shows you the operation process through actual cases. The operation method is simple and fast and practical. I hope this article "how to use thread groups in Java" can help you solve the problem.

Thread Groups in Java (ThreadGroup class)

Java uses the ThreadGroup class to represent a thread group, which represents a collection of threads and can manage a batch of threads and thread groups. Threads can be attributed to a thread group, thread group can have thread objects, there can also be thread groups, groups can also have threads, such an organizational structure is somewhat similar to the form of a tree, as shown in the figure.

All threads created by the user belong to the specified thread group, and if no thread group is explicitly specified, the thread belongs to the default thread group (i.e., the main thread group). By default, child threads and parent threads are in the same thread group.

In addition, the thread group to which a thread belongs can only be specified when it is created, and the thread group to which it belongs cannot be changed midway, that is, once the thread group to which it belongs is specified, it cannot be changed.

II. Why use thread groups

1. security

Threads in the same thread group can modify each other's data. However, if you are in different thread groups, you cannot modify the data "across thread groups," which can ensure data security to a certain extent.

2. Batch management

Threads or thread group objects can be managed in bulk, effectively organizing or controlling them.

III. Thread Group Usage Example

1. Thread associations Thread groups: first level associations

A first-level association is when a parent object has children, but no grandchildren are created. For example, create a thread group, and then create threads belonging to the group, so as to effectively manage these threads. The code example is as follows:

public class ThreadGroupTest { public static void main (String[] args) { ThreadGroup rootThreadGroup = new ThreadGroup ("root thread group"); Thread thread0 = new Thread (rootThreadGroup, new MRunnable(), "Thread A"); Thread thread1 = new Thread (rootThreadGroup, new MRunnable(), "Thread B"); thread0.start (); thread1.start(); }}class MRunnable implements Runnable { @Override public void run() { while (! Thread.currentThread().isInterrupted()) { System.out.println("Thread name: " + Thread.currentThread().getName() + ", Thread group: " + Thread.currentThread().getThreadGroup().getName()) ; try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } }} Copy code

The results are as follows:

Thread name: Thread A, thread group: root Thread group Thread name: Thread B, thread group: root Thread group Copy code

2. Thread associative thread group: multilevel associative

The so-called multi-level association is that there are child objects in the parent object, and then create grandchild objects in the child object, and the effect of descendants will appear. For example, use the second construction method in the figure below to attribute the child thread group to a thread group, and then attribute the created thread to the child thread group, so that there will be the effect of thread tree.

代码示例如下：

public class ThreadGroupTest { public static void main(String[] args) { ThreadGroup rootThreadGroup = new ThreadGroup("root线程组"); Thread thread0 = new Thread(rootThreadGroup, new MRunnable(), "线程A"); Thread thread1 = new Thread(rootThreadGroup, new MRunnable(), "线程B"); thread0.start(); thread1.start(); ThreadGroup threadGroup1 = new ThreadGroup(rootThreadGroup, "子线程组"); Thread thread2 = new Thread(threadGroup1, new MRunnable(), "线程C"); Thread thread3 = new Thread(threadGroup1, new MRunnable(), "线程D"); thread2.start(); thread3.start(); }}class MRunnable implements Runnable { @Override public void run() { while (!Thread.currentThread().isInterrupted()) { System.out.println("线程名: " + Thread.currentThread().getName() + ", 所在线程组: " + Thread.currentThread().getThreadGroup().getName() + ", 父线程组: " + Thread.currentThread().getThreadGroup().getParent().getName()); try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } }}复制代码

执行结果如下：

线程名: 线程A, 所在线程组: root线程组, 父线程组: main线程名: 线程B, 所在线程组: root线程组, 父线程组: main线程名: 线程C, 所在线程组: 子线程组, 父线程组: root线程组线程名: 线程D, 所在线程组: 子线程组, 父线程组: root线程组复制代码

3.批量管理组内线程

使用线程组自然是要对线程进行批量管理，比如可以批量中断组内线程，代码示例如下：

public class ThreadGroupTest { public static void main(String[] args) { ThreadGroup rootThreadGroup = new ThreadGroup("root线程组"); Thread thread0 = new Thread(rootThreadGroup, new MRunnable(), "线程A"); Thread thread1 = new Thread(rootThreadGroup, new MRunnable(), "线程B"); thread0.start(); thread1.start(); ThreadGroup threadGroup1 = new ThreadGroup(rootThreadGroup, "子线程组"); Thread thread2 = new Thread(threadGroup1, new MRunnable(), "线程C"); Thread thread3 = new Thread(threadGroup1, new MRunnable(), "线程D"); thread2.start(); thread3.start(); rootThreadGroup.interrupt(); System.out.println("批量中断组内线程"); }}class MRunnable implements Runnable { @Override public void run() { while (!Thread.currentThread().isInterrupted()) { System.out.println("线程名: " + Thread.currentThread().getName() + ", 所在线程组: " + Thread.currentThread().getThreadGroup().getName() + ", 父线程组: " + Thread.currentThread().getThreadGroup().getParent().getName()); try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); break; } } System.out.println(Thread.currentThread().getName() + "执行结束"); }}复制代码

执行结果如下：

线程名: 线程A, 所在线程组: root线程组, 父线程组: main线程名: 线程B, 所在线程组: root线程组, 父线程组: main线程名: 线程C, 所在线程组: 子线程组, 父线程组: root线程组线程名: 线程D, 所在线程组: 子线程组, 父线程组: root线程组批量中断组内线程线程A执行结束线程B执行结束线程C执行结束线程D执行结束复制代码关于"Java中怎么使用线程组"的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识，可以关注行业资讯频道，小编每天都会为大家更新不同的知识点。

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