Java Program to Call One Constructor from another

Example 1: Java program to call one constructor from another

 class Main { int sum; // first constructor Main() { // calling the second constructor this(5, 2); } // second constructor Main(int arg1, int arg2) { // add two value this.sum = arg1 + arg2; } void display() { System.out.println("Sum is: " + sum); } // main class public static void main(String[] args) { // call the first constructor Main obj = new Main(); // call display method obj.display(); } }

Output

 Sum is: 7

In the above example, we have created a class named Main. Here, you have created two constructors inside the Main class.

 Main() {..} Main(int arg1, int arg2) {...}

Inside the first constructor, we have used this keyword to call the second constructor.

 this(5, 2);

Here, the second constructor is called from the first constructor by passing arguments 5 and 2.

Note: The line inside a constructor that calls another constructor should be the first line of the constructor. That is, this(5, 2) should be the first line of Main().

Example 2: Call the constructor of the superclass from the constructor of the child class

We can also call the constructor of the superclass from the constructor of child class using super().

 // superclass class Languages { // constructor of the superclass Languages(int version1, int version2) { if (version1 > version2) { System.out.println("The latest version is: " + version1); } else { System.out.println("The latest version is: " + version2); } } } // child class class Main extends Languages { // constructor of the child class Main() { // calling the constructor of super class super(11, 8); } // main method public static void main(String[] args) { // call the first constructor Main obj = new Main(); } }

Output

 The latest version is: 11

In the above example, we have created a superclass named Languages and a subclass Main. Inside the constructor of the Main class, notice the line,

 super(11, 8);

Here, we are calling the constructor of the superclass (i.e. Languages(int version1, int version2)) from the constructor of the subclass (Main()).