I was looking at other questions on SO, but I didn't really see an explanation for my question. I read that calling a constructor from another constructor (using the this keyword) was valid, but I didn't understand why it was valid.
Previously, I thought that only one constructor could act per object. Constructor chaining seems to break this logic, in that while calling one constructor, it runs another in conjunction to the original, targeted constructor. Why does constructor chaining work?
We chain (call) one constructor from other within the same class so that we can avoid code duplication. Without chaining every constructor, we end up repeating business details and that leads to code duplication and hard to maintain the code as well.
Imagine you are creating a Bus.
public class Bus {
int noOfSeats;
String busColor;
public Bus() {
this(40); //// Using another constructor and proceeding with default values..
}
public Bus(int seats) {
this(seats,"red"); // Using another constructor and proceeding..
}
public Bus(int seats, String color) {
this.noOfSeats = seats;
this.busColor = color;
}
}
And the person using this class can use only constructor at a time, where as you are using chaining internally. Imagine that you have a method which initializes things with default values and calling it in the constructor. There's nothing wrong in that, right?
Just to clarify, the person who is creating the object is calling only one constructor. The invoked constructor calls others which is internal to that class.