Groovy - Naming a Thread

Name a Thread while Implementing a Runnable Interface

If your class is intended to be executed as a thread and is implementing a Runnable interface. You will need to instantiate a Thread object using the following constructor −

Thread(Runnable threadObj, String threadName);

Where, threadObj is an instance of a class that implements the Runnable interface and threadName is the name given to the new thread.

Once a Thread object is created, you can start it by calling start() method, which executes a call to run( ) method. Following is a simple syntax of start() method −

void start();

Example - Naming a thread

In this example, we're creating a class RunnableDemo by implementing Runnable interface. RunnableDemo class has run() method implementation. In main class TestThread, we've created the RunnableDemo objects and using those objects we've created two Thread objects. When Thread.start() method is called on each thread objects, threads start processing and program is executed.

Example.groovy

class Example {
   static void main(String[] args) {
	  RunnableDemo runnableDemo1 = new RunnableDemo( "Thread-1");
	  RunnableDemo runnableDemo2 = new RunnableDemo( "Thread-2");
	  
	  Thread thread1 = new Thread(runnableDemo1);
	  Thread thread2 = new Thread(runnableDemo2);
	
	  thread1.start();
	  thread2.start();
   }
}
class RunnableDemo implements Runnable {
   private String threadName;
   RunnableDemo( String name) {
      threadName = name;
      println("Thread: " + threadName + ", " + "State: New");
   }
   void run() {
      println("Thread: " + threadName + ", " + "State: Running");
      for(int i = 4; i > 0; i--) {
         println("Thread: " + threadName + ", " + i);         
      }
      println("Thread: " + threadName + ", " + "State: Dead");
   }
}

Output

The above program produces the following output −

Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: Thread-1, State: Running
Thread: Thread-2, State: Running
Thread: Thread-2, 4
Thread: Thread-1, 4
Thread: Thread-2, 3
Thread: Thread-2, 2
Thread: Thread-2, 1
Thread: Thread-1, 3
Thread: Thread-1, 2
Thread: Thread-2, State: Dead
Thread: Thread-1, 1
Thread: Thread-1, State: Dead

Naming a Thread while extending a Thread Class

The second way to create a thread is to create a new class that extends Thread class. This approach provides more flexibility in handling multiple threads created using available methods in Thread class. In order to name the thread, we need to call the super class Thread constructor with name.

class ThreadDemo extends Thread {
   ThreadDemo( String name) {
      super(name);
      ...
   }
...
}

Example - Naming a Thread while extending a Thread Class

Here is the preceding program rewritten to extend the Thread. In this example, we've created a ThreadDemo class which extends Thread class. We're calling super(name) in constructor() method to assign a name to the thread and called super.start() to start the thread processing.

Example.groovy

class Example {
   static void main(String[] args) {
	  ThreadDemo thread1 = new ThreadDemo( "Thread-1");
	  ThreadDemo thread2 = new ThreadDemo( "Thread-2");
	  thread1.start();
	  thread2.start();
   }
}
class ThreadDemo extends Thread {
   ThreadDemo( String name) {
	  super(name);
      println("Thread: " + name + ", " + "State: New");
   }
   void run() {
      println("Thread: " + Thread.currentThread().getName() + ", " + "State: Running");
      for(int i = 4; i > 0; i--) {
         println("Thread: " + Thread.currentThread().getName() + ", " + i); 
      }
      println("Thread: " + Thread.currentThread().getName() + ", " + "State: Dead");
   }

   void start () {
      println("Thread: " + Thread.currentThread().getName() + ", " + "State: Start");
      super.start();
   }
}

Output

The above program produces the following output −

Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: main, State: Start
Thread: main, State: Start
Thread: Thread-1, State: Running
Thread: Thread-2, State: Running
Thread: Thread-1, 4
Thread: Thread-2, 4
Thread: Thread-2, 3
Thread: Thread-2, 2
Thread: Thread-2, 1
Thread: Thread-1, 3
Thread: Thread-1, 2
Thread: Thread-2, State: Dead
Thread: Thread-1, 1
Thread: Thread-1, State: Dead
Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: main, State: Start
Thread: main, State: Start
Thread: Thread-1, State: Running
Thread: Thread-2, State: Running
Thread: Thread-1, 4
Thread: Thread-2, 4
Thread: Thread-1, 3
Thread: Thread-2, 3
Thread: Thread-1, 2
Thread: Thread-2, 2
Thread: Thread-1, 1
Thread: Thread-2, 1
Thread: Thread-1, State: Dead
Thread: Thread-2, State: Dead

Example - Using default name of Thread

In this example, we've created a ThreadDemo class which extends Thread class. We're not passing any name to the Thread and it will print the default names assigned to the threads by the system.

Example.groovy

class TestThread {
   static void main(String[] args) {
	  ThreadDemo thread1 = new ThreadDemo();
	  ThreadDemo thread2 = new ThreadDemo();
	  thread1.start();
	  thread2.start();
   }
}
class ThreadDemo extends Thread {
   ThreadDemo( ) {
      println("Thread: " + Thread.currentThread().getName() + ", " + "State: New");
   }
   public void run() {
      println("Thread: " + Thread.currentThread().getName() + ", " + "State: Running");
      for(int i = 4; i > 0; i--) {
         println("Thread: " + Thread.currentThread().getName() + ", " + i); 
      }
      println("Thread: " + Thread.currentThread().getName() + ", " + "State: Dead");
   }
   public void start () {
      println("Thread: " + Thread.currentThread().getName() + ", " + "State: Start");
      super.start();
   }
}

Output

The above program produces the following output −

Thread: main, State: New
Thread: main, State: New
Thread: main, State: Start
Thread: main, State: Start
Thread: Thread-0, State: Running
Thread: Thread-1, State: Running
Thread: Thread-0, 4
Thread: Thread-1, 4
Thread: Thread-0, 3
Thread: Thread-1, 3
Thread: Thread-0, 2
Thread: Thread-0, 1
Thread: Thread-1, 2
Thread: Thread-1, 1
Thread: Thread-0, State: Dead
Thread: Thread-1, State: Dead