Overload constructor in java

The way of defining multiple constructor with different arguments in a specified class is called constructor overloading. Parameters can differ in type, number or order.

Example

/**
 * This program is used to show the use of constructor overloading.
 * @author W3spoint
 */
public class ConstructorOverload {
       int rollNo;
       boolean isStudent;
       String name;
 
 
       //One argument constructor
       ConstructorOverload(boolean isStudent ){
       System.out.println("One argument constructor called.");
          this.isStudent = isStudent ;
       }               
 
       //Two argument constructor
       ConstructorOverload (int rollNo, String name){
        System.out.println("Two argument constructor called.");
        this.rollNo = rollNo;
        this.name = name;
       }    
 
       //Three argument constructor
       ConstructorOverload (boolean isStudent, int rollNo, String name){
         System.out.println("Three argument constructor called.");
         this.isStudent = isStudent ;
         this.rollNo = rollNo;
         this.name = name;
        }
       public static void main(String args[]){
         //one argument constructor call
         ConstructorOverload obj1 = new ConstructorOverload(true);
 
         //print values of object properties.
         System.out.println("isStudent = " + obj1.isStudent);
         System.out.println("Roll No = " + obj1.rollNo);
         System.out.println("Name = " + obj1.name); 
 
         //two argument constructor call
         ConstructorOverload obj2 = new ConstructorOverload(11, "Jai");
 
          //print values of object properties.
          System.out.println("isStudent = " + obj2.isStudent);
          System.out.println("Roll No = " + obj2.rollNo);
          System.out.println("Name = " + obj2.name);
 
          //three argument constructor call
          ConstructorOverload obj3 = new ConstructorOverload(true, 22, "Roxy");
 
          //print values of object properties.
          System.out.println("isStudent = " + obj3.isStudent);
          System.out.println("Roll No = " + obj3.rollNo);
          System.out.println("Name = " + obj3.name);
        }
}

Output

One argument constructor called. 
isStudent = true 
Roll No = 0 
Name = null
Two argument constructor called. 
isStudent = false      
Roll No = 11 
Name = Jai 
Three argument constructor called. 
isStudent = true 
Roll No = 22
Name = Roxy

Java interview questions on constructor

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