How to simplify similar constructors?

Question

How can I simplify this:

Is it necessary to have two different constructors with just one little difference.

Is there a way to simplify that using just one of them?

public class MyCostructor {

    public MyCostructor(int w, int h, String name) {
         this.w = w;
         this.h = h;
         this.name = name;
    }
    
    public MyCostructor(int w, int h) {
         this.w = w;
         this.h = h;
    }
}

score 6 · Answer 1 · answered Apr 24 '14 at 15:20

6

Yes you can use the keyword this to call another constructor and you respect the DRY principle (don't repeat yourself).

public MyCostructor(int w, int h){ 
   this(w,h,null);
}

You can read more here (section Using this with a Constructor)

answered Apr 24 '14 at 15:20

Alexis C.

91,686
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score 3 · Answer 2 · answered Apr 24 '14 at 15:20

3

Use this() in your constructor:

public MyCostructor(int w, int h, String name) {
    this(w, h);
    this.name = name;
}

public MyCostructor(int w, int h) {
    this.w = w;
    this.h = h;
}

answered Apr 24 '14 at 15:20

Luiggi Mendoza

85,076
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2

usual practice is to call `this()` from constructor with less arguments – Iłya Bursov Apr 24 '14 at 15:22
@Lashane yes, but in this case there's no need to set `this.name = null;` since that's the default value. Besides, IMO sending `null` as parameter is not quite right (even if it does the right job), do you? – Luiggi Mendoza Apr 24 '14 at 15:23
@Luiggi Mendoza so you mean it is not possible to do everything with only one constructor, right? I mean.. **in a game** I want to create a car with a yellow dot in the front and another equal car without the dot, two constructors are necessary in that case? – user3569452 Apr 24 '14 at 15:29
@user3569452 sadly, yes. You can only simplify the way you implement the constructors using `this()` as the first line of the constructor. – Luiggi Mendoza Apr 24 '14 at 15:30
@user3569452 it is depends on your class structure, you can define "dot" as optional attribute and just provide getters/setters for it, also take look at builders and chaining http://stackoverflow.com/questions/17171012/how-to-avoid-constructor-code-redundancy-in-java – Iłya Bursov Apr 24 '14 at 15:31

How to simplify similar constructors?

2 Answers2