The ThreadGroup method isDaemon() used to determine whether a thread group is a daemon thread group. It returns a boolean value true, if thread group is daemon group. A daemon thread group is automatically destroyed when its last thread is stopped or its last thread group is destroyed.
Note : 'isDaemon()' is deprecated and marked for removal, from version 16.
1 public final boolean isDaemon()
return : It returns a boolean value that specifies whether thread group is daemon thread group or not.
1 package com.java;
2
3 class CustomThread extends Thread {
4
5 public void run() {
6 System.out.println("Starting thread : " + this.getName());
7 }
8 }
A CustomThread class is created by extending a Thread class and overriding a run() method. Once a thread instance method start() called, it executes run() method.
ThreadGroup method isDaemon()
1 package com.java;
2
3 public class Example extends Thread {
4
5 public static void main(String[] args) {
6
7 CustomThread ct = new CustomThread();
8 ThreadGroup tg = new ThreadGroup("TG1");
9
10
11 Thread t1 = new Thread(tg, ct, "T1");
12 t1.start();
13
14 System.out.println("Is ThreadGroup isDaemon : " + tg.isDaemon());
15 }
16 }
In the above example, a CustomThread and ThreadGroup objects are created. An instance of Thread class is created by passing a thread group, thread object and thread name. A thread starts by calling start() method that executes CustomThread run() method. A ThreadGroup method isDaemon() is called that returns false, as it is not a daemon thread group.
1 Starting thread : Thread-0
2 Is ThreadGroup isDaemon : false
Example 2 with internal thread class
Example 2 with internal thread class
1 package com.java;
2
3 class CustomThread extends Thread {
4
5 public void run() {
6 System.out.println("CustomThread thread started...");
7 }
8 }
9
10 public class Example {
11
12 public static void main(String[] args) {
13 CustomThread ct = new CustomThread();
14 ThreadGroup tg = new ThreadGroup("TG1");
15 tg.setDaemon(true);
16
17 Thread t1 = new Thread(tg, ct, "T1");
18 t1.start();
19
20 System.out.println("Is ThreadGroup isDaemon : " + tg.isDaemon());
21 }
22 }
In the above example, a CustomThread class is created by extending a Thread class. A Thread class is created by passing a CustomThread class and ThreadGroup class. A ThreadGroup method setDaemon() method called by passing a boolean value true. A ThreadGroup method isDaemon() called that returns boolean value true.
1 CustomThread thread started...
2 Is ThreadGroup isDaemon : true
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