18 Jan Java Threading

Threading in Java means working on more than two things at the same time. For achieving Threading, Java has the Thread class. The Thread class has constructors and methods to work in Threads in Java.

Thread Constructors

The following are the constructors in Java Threading:

Thread Methods

The following are the methods in Java Threading:

Create a Thread in Java

To create a Thread in Java:

• Create a Thread by extending the Thread class
• Create a Thread by implementing the Runnable interface

Create a Thread by extending the Thread class

We can create a Thread by extending and running the Thread class it using the start() method. Let us see an example:

class Studyopedia extends Thread {  

  public void run(){  
    System.out.println("The thread is running");  
  }  
  public static void main(String args[]){  
    Studyopedia th = new Studyopedia();  
    
    // The start() method starts the execution of the thread
    th.start();  
 }  
}

Output

The thread is running

Let us understand the above code:

• class Studyopedia extends Thread { → Defines a class Studyopedia that inherits from Java’s built-in Thread class.
• public void run(){ → Overrides the run() method, which contains the code that will execute when the thread runs.
• System.out.println("The thread is running"); → Prints a message to the console when the thread is active.
• public static void main(String args[]){ → Entry point of the program; execution starts here.
• Studyopedia th = new Studyopedia(); → Creates a new thread object named th.
• th.start(); → Starts the thread. This internally calls the run() method in a new thread of execution.

Create a Thread by implementing the Runnable interface

We can create a Thread by implementing the Runnable interface and running it using the start() method.

The Runnable interface in Java is a functional interface from the java.lang package that represents a task to be executed by a thread. It defines a single abstract method run(), which contains the code that runs concurrently.

Runnable is generally preferred over extending Thread because:

• Flexibility in inheritance: Java allows only single inheritance. If you extend Thread, your class cannot extend any other class. By implementing Runnable, your class remains free to extend another class while still defining concurrent behavior.
• Separation of concerns: Implementing Runnable cleanly separates the task (the run() method) from the thread management. The Thread class then takes care of execution, while your class focuses only on the logic of the task.

Let us see an example:

// Runnable is preferred because it allows a class to extend another class while still running tasks concurrently.
class Studyopedia implements Runnable{  

  public void run(){  
    System.out.println("The thread is running");  
  }  
  public static void main(String args[]){  
    Studyopedia s = new Studyopedia();  
    Thread th = new Thread(s);  
    
    // The start() method starts the execution of the thread
    th.start();  
 }  
}

Output

The thread is running

Let us understand the above code:

• class Studyopedia implements Runnable { → Declares a class Studyopedia that implements the Runnable interface.
• public void run(){ → Defines the run() method required by Runnable.
• System.out.println("The thread is running"); → Prints a message when the thread executes.
• public static void main(String args[]){ → Program execution begins here.
• Studyopedia s = new Studyopedia(); → Creates an Studyopedia object, which is a Runnable.
• Thread th = new Thread(s); → Creates an Thread object and passes s as the target task.
• th.start(); → Starts the new thread, which internally calls run().

Comparison

Let us compare both the methods we saw above to create threads in Java:

Threads vs Process

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