how to create a thread in java: source code example

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How to create one or more threads in Java with a few lines of code. Free source code examples with simple instant solutions.

starting point: a simple java program, having just one thread - the main thread.

public class csj01x1 
{
   public static void main(String args[]) throws Throwable  
   {
      new csj01x1().myfunc();
   }

   void myfunc() throws Throwable
   {
      for (int i=0; i<100; i++) {
         System.out.println("thread "
            +Thread.currentThread().getName()+" step "+i);
         Thread.sleep(500);
      }
   }
}

output:

   thread main step 0
   thread main step 1
   thread main step 2
   thread main step 3
   ...

solution 01: creating two parallel threads by implementing the Runnable interface, i.e. adding a "run" method.

public class csj01x2 implements Runnable
{
   public static void main(String args[]) throws Throwable  
   {
      csj01x2 obj1 = new csj01x2();
      csj01x2 obj2 = new csj01x2();
      new Thread(obj1).start();
      new Thread(obj2).start();
      // main thread is ending here,
      // Thread-0 and Thread-1 continue to run.
   }

   public void run()
   {
      try {
         for (int i=0; i<100; i++) {
            System.out.println("thread "
               +Thread.currentThread().getName()+" step "+i);
            Thread.sleep(500);
         }
      } catch (Throwable t) { }
   }
}

output:

   thread Thread-0 step 0
   thread Thread-1 step 0
   thread Thread-0 step 1
   thread Thread-1 step 1
   thread Thread-0 step 2
   thread Thread-1 step 2
   thread Thread-0 step 3
   thread Thread-1 step 3
   ...

solution 02: alternatively, we may create two parallel threads by deriving our class from the "Thread" class. in this case, we also have to provide a "run" method, because Thread uses the Runnable interface.

public class csj01x3 extends Thread
{
   public static void main(String args[]) throws Throwable  
   {
      new csj01x3().start();
      new csj01x3().start();
      // main thread is ending here,
      // Thread-0 and Thread-1 continue to run.
   }

   public void run()
   {
      try {
         for (int i=0; i<100; i++) {
            System.out.println("thread "
               +Thread.currentThread().getName()+" step "+i);
            Thread.sleep(500);
         }
      } catch (Throwable t) { }
   }
}

this produces the same output as solution 01, but it has one tradeoff: as we derive our class from Thread, we can no longer derive it from anything else. therefore solution 01 is more flexible.