Question

Suppose you have a class with this constructor:

public SomeObj(int x, int y) {
    this.x = x;
    this.y = y;
}

All good. But now if you want to clone the object, I want a constructor to accept one argument with an object from that type, so inside the constructor all (necessary) fields can be copied.

public SomeObj(SomeObj objectToClone) { ... }

But now which of the following two ways is better? What are the advantages and disadvantages (performance (byte code), readability…)?

// 1
public SomeObj(SomeObj objectToClone) {
    this.x = objectToClone.x;
    this.y = objectToClone.y;
}

// 2
public SomeObj(SomeObj objectToClone) {
    this(objectToClone.x, objectToClone.y);
}

Answer 1

I would go with the latter, personally.

Where possible, I try to make exactly one constructor have a “real” body, and make all others delegate to it. That’s not always possible – in particular, different constructors may need to delegate to different superconstructors – but it’s nice knowing there’s one place you can put extra initialization, logging, breakpoints etc which will always get hit.