How do I call one constructor from another in Java?

Question

Is it possible to call a constructor from another (within the same class, not from a subclass)? If yes how? And what could be the best way to call another constructor (if th

Answer 1

Yes it is possible to call one constructor from another. But there is a rule to it. If a call is made from one constructor to another, then

that new constructor call must be the first statement in the current constructor

public class Product {
     private int productId;
     private String productName;
     private double productPrice;
     private String category;

    public Product(int id, String name) {
        this(id,name,1.0);
    }

    public Product(int id, String name, double price) {
        this(id,name,price,"DEFAULT");
    }

    public Product(int id,String name,double price, String category){
        this.productId=id;
        this.productName=name;
        this.productPrice=price;
        this.category=category;
    }
}

So, something like below will not work.

public Product(int id, String name, double price) {
    System.out.println("Calling constructor with price");
    this(id,name,price,"DEFAULT");
}

Also, in the case of inheritance, when sub-class's object is created, the super class constructor is first called.

public class SuperClass {
    public SuperClass() {
       System.out.println("Inside super class constructor");
    }
}
public class SubClass extends SuperClass {
    public SubClass () {
       //Even if we do not add, Java adds the call to super class's constructor like 
       // super();
       System.out.println("Inside sub class constructor");
    }
}

Thus, in this case also another constructor call is first declared before any other statements.