Java - this keyword

this keyword is a very important keyword to identify an object. Following are the usage of this keyword.

• this can be used to get the current object.

• this can be used to invoke current object's method.

• this() can be used to invoke current class constructor.

• this can be passed as a parameter to a method call.

• this can be passed as a parameter to a constructor.

• this can be used to return the current object from the method.

Following example shows a simple usecase of this keyword.

Example

public class JavaTester {
   private String message;
   public JavaTester(String message){
      this.message = message;
   }
   public void printMessage(){
      System.out.println(message);
   }
   public static void main(String args[]) {
      JavaTester tester = new JavaTester("Hello World");
      tester.printMessage();
   }
}

Compile and run the above program. This will produce the following result −

Output

Hello World

Following example shows a usecase of this keyword in case of inheritance.

Example

class Superclass {
   int age;

   Superclass(int age) {
      this.age = age; 		 
   }

   public void getAge() {
      System.out.println("The value of the variable named age in super class is: " +age);
   }
}

public class Subclass extends Superclass {
   Subclass(int age) {
      super(age);
   }

   public static void main(String args[]) {
      Subclass s = new Subclass(24);
      s.getAge();
   }
}

Output

Compile and execute the above code using the following syntax.

javac Subclass
java Subclass

In this example, we're referring to current object in SuperClass constructor using this keyword.