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Java - ThreadGroup isDaemon() Method with Examples
Description
The Java ThreadGroup isDaemon() method tests if this thread group is a daemon thread group. A daemon thread group is automatically destroyed when its last thread is stopped or its last thread group is destroyed.
Declaration
Following is the declaration for java.lang.ThreadGroup.isDaemon() method
public final boolean isDaemon()
Parameters
NA
Return Value
This method returns true if this thread group is a daemon thread group, false otherwise.
Exception
NA
Example 1
The following example shows the usage of ThreadGroup isDaemon() method in case of a single ThreadGroup object. We've created a ThreadGroup object and assigned it a name. Then we've created two threads using the threadgroup object created earlier. Using isDaemon() method, we're getting the status of the parent of this thread group object which will be false as default.
package com.tutorialspoint; public class ThreadGroupDemo implements Runnable { public static void main(String[] args) { ThreadGroupDemo tg = new ThreadGroupDemo(); tg.start(); } public void start() { try { // create a ThreadGroup ThreadGroup threadGroup = new ThreadGroup("ThreadGroup"); // create a thread Thread t1 = new Thread(threadGroup, this); System.out.println("Starting " + t1.getName() + "..."); t1.start(); // create another thread Thread t2 = new Thread(threadGroup, this); System.out.println("Starting " + t2.getName() + "..."); t2.start(); // returns the status of thread group boolean isDaemon = threadGroup.isDaemon(); System.out.println("Status of the threadGroup = " + isDaemon); // block until the other threads finish t1.join(); t2.join(); } catch (InterruptedException ex) { System.out.println(ex.toString()); } } // implements run() public void run() { for(int i = 0; i < 4;i++) { i++; try { Thread.sleep(50); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.println(Thread.currentThread().getName() + " finished executing."); } }
Output
Let us compile and run the above program, this will produce the following result −
Starting Thread-0... Starting Thread-1... Status of the threadGroup = false Thread-1 finished executing. Thread-0 finished executing.
Example 2
The following example shows the usage of ThreadGroup isDaemon() method in case of multiple ThreadGroup objects. We've created a ThreadGroup object and assigned it a name. As next, we've created a child ThreadGroup object. Then we've created two threads using the threadgroup objects created earlier. Using isDaemon() method, we're printing status each threadgroup object.
package com.tutorialspoint; public class ThreadGroupDemo implements Runnable { public static void main(String[] args) { ThreadGroupDemo tg = new ThreadGroupDemo(); tg.start(); } public void start() { try { // create a parent ThreadGroup ThreadGroup pThreadGroup = new ThreadGroup("parent ThreadGroup"); // create a child ThreadGroup for parent ThreadGroup ThreadGroup cThreadGroup = new ThreadGroup(pThreadGroup, "child ThreadGroup"); // create a thread Thread t1 = new Thread(pThreadGroup, this); System.out.println("Starting " + t1.getName() + "..."); t1.start(); // create another thread Thread t2 = new Thread(cThreadGroup, this); System.out.println("Starting " + t2.getName() + "..."); t2.start(); // returns the status of thread group System.out.println("Status of pThreadGroup = " + pThreadGroup.isDaemon()); System.out.println("Status of cThreadGroup = " + cThreadGroup.isDaemon()); // block until the other threads finish t1.join(); t2.join(); } catch (InterruptedException ex) { System.out.println(ex.toString()); } } // implements run() public void run() { for(int i = 0; i < 4;i++) { i++; try { Thread.sleep(50); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.println(Thread.currentThread().getName() + " finished executing."); } }
Output
Let us compile and run the above program, this will produce the following result −
Starting Thread-0... Starting Thread-1... Status of pThreadGroup = false Status of cThreadGroup = false Thread-1 finished executing. Thread-0 finished executing.
Example 3
The following example shows the usage of ThreadGroup isDaemon() method in case of child and grandchild ThreadGroup objects. We've created a ThreadGroup object and assigned it a name. As next, we've created a child ThreadGroup object. Then we've created two threads using the child and grandchild threadgroup objects created earlier. Using isDaemon() method, we're printing status of each threadgroup object.
package com.tutorialspoint; public class ThreadGroupDemo implements Runnable { public static void main(String[] args) { ThreadGroupDemo tg = new ThreadGroupDemo(); tg.start(); } public void start() { try { // create a parent ThreadGroup ThreadGroup pThreadGroup = new ThreadGroup("Parent ThreadGroup"); // create a child ThreadGroup for parent ThreadGroup ThreadGroup cThreadGroup = new ThreadGroup(pThreadGroup, "Child ThreadGroup"); // create a grandchild ThreadGroup for parent ThreadGroup ThreadGroup gThreadGroup = new ThreadGroup(cThreadGroup, "GrandChild ThreadGroup"); // create a thread Thread t1 = new Thread(cThreadGroup, this); System.out.println("Starting " + t1.getName() + "..."); t1.start(); // create another thread Thread t2 = new Thread(gThreadGroup, this); System.out.println("Starting " + t2.getName() + "..."); t2.start(); // returns the status of thread group System.out.println("Status of pThreadGroup = " + pThreadGroup.isDaemon()); System.out.println("Status of cThreadGroup = " + cThreadGroup.isDaemon()); System.out.println("Status of gThreadGroup = " + gThreadGroup.isDaemon()); // block until the other threads finish t1.join(); t2.join(); } catch (InterruptedException ex) { System.out.println(ex.toString()); } } // implements run() public void run() { for(int i = 0; i < 4;i++) { i++; try { Thread.sleep(50); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.println(Thread.currentThread().getName() + " finished executing."); } }
Output
Let us compile and run the above program, this will produce the following result −
Starting Thread-0... Starting Thread-1... Status of pThreadGroup = false Status of cThreadGroup = false Status of gThreadGroup = false Thread-0 finished executing. Thread-1 finished executing.
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