CODEWITHSUNDEEP
javaabstract-classcomparable
Luis Valdez
Luis Valdez

Reputation: 2429

Problem Overriding method from Comparable Interface

I have an abstract class named Individuo that implements the Comparable<Individuo> interface. Yet when I try to override the method in the child classes it implements the following method:

@Override
public int compareTo(Object o) {
    return 0;
}

Shouldn't it implement the following?

@Override
public int compareTo(Individuo o) {
    return 0;
}

Here are the declarations

Individuo:

public abstract class Individuo<I extends Individuo> implements Cloneable, Comparable<Individuo>

Individuo_MultiOOP (child):

public class Individuo_MultiOOP extends Individuo implements Cloneable

Upvotes: 0

Views: 196

Answers (4)

Haripriya
Haripriya

Reputation: 1000

Edit 2 (after question update)

Since Individuo is declared with generic type so use Comparable<Individuo<I>>
instead of Comparable<Individuo> in declaration.

Original answer
First save the class with implementing declaration without overriding compareTo() -

public class IndividuoChild extends Individuo {
...
}

Then from Compiler error note [can be found in IDEs like eclipse, intellij], select "Add unimplemented methods" which will generate expected compareTo() as -

@Override
public int compareTo(Individuo o) {
    // TODO Auto-generated method stub
    return 0;
}

Upvotes: 1

Huy Nguyen
Huy Nguyen

Reputation: 2061

No, you should override with same argument. It will be more readability and easily to understand.

class Individuo implements Comparable<Individuo>{
    @Override
    public int compareTo(Individuo o) {
        return 0;
    }
}

Child class

public class Child extends Individuo{
    @Override
    public int compareTo(Individuo o) {
        // TODO Auto-generated method stub
        return 0;
    }
}

If you use Object, the design maybe a problem.

Upvotes: 0

Andrew
Andrew

Reputation: 49656

It's likely that the children extend a raw version of Individuo which is generalised by some arguments.

In this case, compareTo(Object o) in the children will compile:

abstract class Individuo<T> implements Comparable<Individuo<T>> {}

class Child extends Individuo {
    @Override
    public int compareTo(Object o) {
        return 0;
    }
}

Make sure the children extend a correct Individuo with all generic parameters provided:

class Child extends Individuo<Child> {
    @Override
    public int compareTo(Object o) { // this shouldn't compile
        return 0;
    }
}

Upvotes: 0

Joe
Joe

Reputation: 341

@Override
public int compareTo(Individuo o) {
    return 0;
}

This is the method which needs to be overridden, if you have specified the generic type. I mean when your class signature is:

public class Individuo implements Comparable < Individuo >

But in cases you have not specified the generic type of comparable interface, it's OK to override public int compareTo(Object o) method. I mean in the case your class signature is:

public class Individuo implements Comparable

Let me know if your issue is resolved bro

Upvotes: 0

Related Questions