Create Threads in Java

By Himanshu Sharma

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Multithreading can be viewed as a digital world’s term for multi-tasking. When someone say they are multitasking, they are performing multiple different tasks within a timeframe.

Even though it is an advanced topic, its use can be observed in our day-to-day basic tasks –

• If you are working on a text editor, there are multiple tasks happening while you are typing like editor is rendering what you have written so far and also saving the same in the file system.

• If you are listening to music or watching videos, rendering of UI (seek bar, play/pause), downloading the song from the internet, using your current selection for suggestions in future.

Multi-tasking in Java can be achieved using Threads and thus the word Multithreading since Threads are responsible for performing multiple tasks in hand.

Let’s start with some basic Thread definition and approaches to create Threads in Java.

Thread:

A thread can be viewed as a lightweight representative (sub-process) of a process. A process can generate one or more threads in order to achieve the desired result. In above examples, text editor and video players are processes.

One of the below three approaches can be used to create thread in Java.

Lambda Expression:

  Thread lambdaThread = new Thread(() -> {
      Thread.currentThread().setName("Lambda-Thread");
      System.out.println("Printing message from Lambda Thread :: "  + Thread.currentThread().getName());
  });
 

Extend Thread Class:

  class CustomThread extends Thread {
  
    @Override
    public void run() {
      this.setName("Custom-Thread");
      System.out.println("Printing message from Custom Thread :: "  + this.getName());
    }
  }
 

Implement Runnable Interface:

  class RunnableThread implements Runnable {
  
    @Override
    public void run() {
      Thread.currentThread().setName("Runnable-Thread");
      System.out.println("Printing message from Runnable Thread :: "  + Thread.currentThread().getName());
    }
  }
 

Above code snippets will allow us to create Thread, but we still have to start these threads in order to execute the code defined in run() method. And for that we need to create objects of our Thread classes (except Lambda approach) and initiate start() method. Refer below code snippet for the same.

  CustomThread customThread = new CustomThread();
  Thread runnableThread = new Thread(new RunnableThread());
  
  customThread.start();
  lambdaThread.start();
  runnableThread.start();
 

If you observe there are some subtle differences-

• Lambda approach is helpful, if you have few lines of codes to be executed in a thread and is not looking for a dedicated java class to maintain.
• If you go with extend Thread class, you should be sure that you don’t want to use your business class to extend any other class since in java you can only extend with one class. Also, this approach gives you the thread object control and thus you don’t need to invoke static methods for getname() and setname() methods.
• Implement runnable approach is the most recommended one, since it gives you all the thread flexibility and also allows you to extend any other class if required in future.