Question

Class A can implement multiple interfaces.

What I do not understand is what happens in this case:

public interface example1 {
    void checkInt(int a);
}

public interface example2 {
    void checkInt(int b);
}

public class class1 implements example1,example2 {
    void checkInt(int c){
        System.out.print(c);
    }
    this.checkint(5);
}

I tried to run it, and it gives me compilation errors. But my question is in general, can I implement two interfaces, that have a functions with the same signature?

Answer 1

What compilations errors are you getting? Because this.checkint is in the wrong case, it should be checkInt(5) ? Also you’re reducing the scope of the method from implied public (as all interface methods are) to default (packaged protected). The checkInt method needs to be public in the implementing class.

Both interfaces define the method, but this is fine as there is one implementation on class1. So class1 fulfils the implemented methods of each interface with its implementation of checkInt(int i). With interfaces you’re only fulfilling a contract, so there is no ambiguity about which method to call – if you work with references of type example1 or example2 it will still be the same checkInt method on class1 which gets invoked.