Local chaining of constructors

[Patrick Haley]

While studying for the SCJP Exam, I read about this technique, which appears to be quite nifty, but I'm wondering what practical purpose it would serve.

Has anyone locally chained constructors in applied code and, if so, to what end?

Thanks.

[C Broussard]

When you say locally chain constructors, are you talking about overriding constructor signatures?


like

public class someobject{
int someobject_value = 0;
public someobject(){
someobject(1);
}
public someobject(int i){
someobject_value = i;
}
}


if this is what you're talking about then yes, this is perfectly
acceptable.

hope that helped.

www.binaryfrost.com

[Jeff Albertson]

That's right, although defining more than one constructor isn't "overriding",
it's just defining more than one constructor, and the syntax is:

public class SomeObject {
    private int value = 0;
 
    public SomeObject(){
        [B]this[/B](1);
    }
 
    public SomeObject(int value){
        this.value = value;
    }
}

[Ken Blair]

Has anyone locally chained constructors in applied code and, if so, to what end?

Often times you may want several constructors for convenience. By chaining them you can keep the bulk of the code in one constructor.

[Brian Cole]

Originally posted by Patrick Haley:
Has anyone locally chained constructors in applied code and, if so, to what end?

Here's some real-world code I wrote the other day.
See if the chaining makes sense to you.

  public GradientPropertyEditorPanelSupport() {
    this(Color.blue); // default to blue
  }
 
  public GradientPropertyEditorPanelSupport(Color c) {
    this(c.getRed(), c.getGreen(), c.getBlue());
  }
 
  public GradientPropertyEditorPanelSupport(int r, int g, int b) {
    Color transparent = new Color(r, g, b, 0);
    // then it does some stuff with 'transparent'
  }