java - Explanation on “this” statement

Question

I am really confused about the outcome of the following program. Could anyone explain it?

public class Prg {
    Prg () {
        this(0);
        System.out.println("Hi ");
    }

    Prg (int x) {
        this(0, 0);
        System.out.println("Hello");
    }

    Prg (int x, int y) {
        System.out.println("How are you");
    }

    public static void main(String[] args) {
        Prg ob = new Prg ();
    }
}

Output:

How are you
Hello
Hi

please stick to the naming Conventions! especially as a Beginner! — Philipp Sander, Dec 19 '16 at 08:59
Note: Java language conventions require that class names start with a capital letter. Throughout this program, `prg` should be changed to `Prg`. Preferably, to a more reasonable name. — RealSkeptic, Dec 19 '16 at 09:00
I fixed it. Ain't I a nice cat? (I'm also fishing for hats.) — Bathsheba, Dec 19 '16 at 09:05

score 1 · Answer 1 · answered Dec 19 '16 at 08:59

1

this(0); is an example of constructor delegation. Here you're calling, from a constructor, the constructor that takes an pair of ints as an argument. To exploit this idiom, the call to another constructor must be the first statement of the calling constructor.

The rest of the behaviour is adequately explained with a line by line debugger.

answered Dec 19 '16 at 08:59

Bathsheba

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suppose if I never used the second this(0, 0). It shows the output as "Hello Hai" – geetha Dec 19 '16 at 09:14

java - Explanation on “this” statement

1 Answers1