When should I use the keyword ‘this’ in a Java class?

The this is a keyword in Java which is used as a reference to the object of the current class, within an instance method or a constructor. Using this you can refer the members of a class such as constructors, variables, and methods.

Example

Live Demo

 public class This_Example { // Instance variable num int num = 10; This_Example() { System.out.println("This is an example program on keyword this"); } This_Example(int num) { // Invoking the default constructor this(); // Assigning the local variable num to the instance variable num this.num = num; } public void greet() { System.out.println("Hi Welcome to Tutorialspoint"); } public void print() { // Local variable num int num = 20; // Printing the local variable System.out.println("value of local variable num is : "+num); // Printing the instance variable System.out.println("value of instance variable num is : "+this.num); // Invoking the greet method of a class this.greet(); } public static void main(String[] args) { // Instantiating the class This_Example obj1 = new This_Example(); // Invoking the print method obj1.print(); // Passing a new value to the num variable through parametrized constructor This_Example obj2 = new This_Example(30); // Invoking the print method again obj2.print(); } } 

Output

 This is an example program on keyword this value of local variable num is : 20 value of instance variable num is : 10 Hi Welcome to Tutorialspoint This is an example program on keyword this value of local variable num is : 20 value of instance variable num is : 30 Hi Welcome to Tutorialspoint