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Java - ThreadGroup getParent() Method
Description
The Java ThreadGroup getParent() method returns the name of the parent thread group of this thread group.
Declaration
Following is the declaration for java.lang.ThreadGroup.getParent() method
public final ThreadGroup getParent()
Parameters
NA
Return Value
This method returns the parent of this thread group. The top-level thread group is the only thread group whose parent is null.
Exception
NA
Example 1
The following example shows the usage of ThreadGroup getParent() 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 getParent() method, we're getting the name of the parent of this thread group object which will be main.
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 name of parent of thread group String name = threadGroup.getParent().getName(); System.out.println("Name of parent of the threadGroup = " + name); // 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... Name of parent of the threadGroup = main Thread-1 finished executing. Thread-0 finished executing.
Example 2
The following example shows the usage of ThreadGroup getParent() 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 getParent() method, we're printing name of parent 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 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 name of thread group String name = pThreadGroup.getParent().getName(); System.out.println("Name of parent of pThreadGroup = " + name); name = cThreadGroup.getParent().getName(); System.out.println("Name of parent of cThreadGroup = " + name); // 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... Name of parent of pThreadGroup = main Name of parent of cThreadGroup = parent ThreadGroup Thread-0 finished executing. Thread-1 finished executing.
Example 3
The following example shows the usage of ThreadGroup getParent() 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 getParent() method, we're printing name of the parent 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 name of the parent of thread group String name = pThreadGroup.getParent().getName(); System.out.println("Name of pThreadGroup = " + name); name = cThreadGroup.getParent().getName(); System.out.println("Name of cThreadGroup = " + name); name = gThreadGroup.getParent().getName(); System.out.println("Name of gThreadGroup = " + name); // 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... Name of pThreadGroup = main Name of cThreadGroup = Parent ThreadGroup Name of gThreadGroup = Child ThreadGroup Thread-1 finished executing. Thread-0 finished executing.
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