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Java - ThreadGroup activeGroupCount() Method
Description
The Java ThreadGroup activeGroupCount() method returns an estimate of the number of active groups in this thread group.
Declaration
Following is the declaration for java.lang.ThreadGroup.activeGroupCount() method
public int activeGroupCount()
Parameters
NA
Return Value
This method returns the number of active thread groups with this thread group as an ancestor.
Exception
NA
Getting Active Group Count in a ThreadGroup Object Example
The following example shows the usage of ThreadGroup activeGroupCount() 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 activeGroupCount() method, we're printing the active group count.
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(); // display the number of active threads System.out.println("Active groups in \"" + threadGroup.getName() + "\" = " + threadGroup.activeGroupCount()); // 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."); } }
Let us compile and run the above program, this will produce the following result −
Starting Thread-0... Starting Thread-1... Active groups in "ThreadGroup" = 0 Thread-1 finished executing. Thread-0 finished executing.
Getting Active Group Count in Multiple ThreadGroup Objects Example
The following example shows the usage of ThreadGroup activeGroupCount() 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 activeGroupCount() method, we're printing the active group count in parent ThreadGroup object as well as in child 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(); // display the number of active threads System.out.println("Active groups in \"" + pThreadGroup.getName() + "\" = " + pThreadGroup.activeGroupCount()); System.out.println("Active groups in \"" + cThreadGroup.getName() + "\" = " + cThreadGroup.activeGroupCount()); // 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."); } }
Let us compile and run the above program, this will produce the following result −
Starting Thread-0... Starting Thread-1... Active groups in "Parent ThreadGroup" = 1 Active groups in "Child ThreadGroup" = 0 Thread-1 finished executing. Thread-0 finished executing.
Getting Active Group Count in Child/GrandChild ThreadGroup Object Example
The following example shows the usage of ThreadGroup activeGroupCount() 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 activeGroupCount() method, we're printing the active group count in all ThreadGroup objects.
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(); // display the number of active threads System.out.println("Active groups in \"" + pThreadGroup.getName() + "\" = " + pThreadGroup.activeGroupCount()); System.out.println("Active groups in \"" + cThreadGroup.getName() + "\" = " + cThreadGroup.activeGroupCount()); System.out.println("Active groups in \"" + gThreadGroup.getName() + "\" = " + gThreadGroup.activeGroupCount()); // 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."); } }
Let us compile and run the above program, this will produce the following result −
Starting Thread-0... Starting Thread-1... Active groups in "Parent ThreadGroup" = 2 Active groups in "Child ThreadGroup" = 1 Active groups in "GrandChild ThreadGroup" = 0 Thread-0 finished executing. Thread-1 finished executing.
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