Java interface with different method parameters

Question

I want to have an interface that allows me to use methods with different parameters. Suppose I have an interface:

public interface Stuff {
 public int Add();
 }

And I have two classes A and B who implement the interface.

public class CLASS A implements Stuff{
 public int Add(int id);
} 
public class CLASS B implements Stuff{
 public int Add(String name);
}

How can I achieve this?

Answer 1

You can write a generic interface for adding some type, something like this:

public interface Addable<T> {
 public int add(T value);
}

and then implement it via

public class ClassA implements Addable<Integer> {
 public int add(Integer value) {
 ...
 }
}
public class ClassB implements Addable<String> {
 public int add(String value) {
 ...
 }
}

• station: How do you call this polymorphically
• khelwood: @station Same way you'd call anything else polymorphically.

Answer 2

either overload the methods:

public interface Stuff {
 public int add(String a);
 public int add(int a);
 }

or check something in common in the inheritance

public interface Stuff {
 public int add(Object a);
 }

or use generics

public interface Stuff<T> {
 public int add(T a);
 }

• user10613856: Both options is usable but personally i would prefer generics.

Answer 3

you need to override the method

public class CLASS A implements Stuff{
 public int add(int a ,int b){
 int result=a+b;
 return result;
 }
 public static void main(String[] args) {
 // TODO Auto-generated method stub
 A ab=new A();
 ab.add(3, 4);
 System.out.println(ab.add(3, 4));
 }
}

Is this you want?