java 接口方法从子类中移除

Question

Anyone provide suggestion for below mentioned:

in java8 consider an interface having two methods (eg interface1,interface 2) implementing those to many subclass later i want to remove one method interface1 from one of my subclass without affecting other is any possible solution is there?

Answer 1

If your subclass declares that it implements this interface, then you have no choice but to provide implementations for all methods, or declare the class abstract. If you want a concrete class which however does not functionally implement all methods in the interface, then here is one option:

public interface YourInterface {
    void method1();
    void method2();
}

public class YourSubClass implements YourInterface {
    @Override
    public void method1() {
        // actually do something
    }

    @Override
    public void method2() {
        throw new UnsupportedOperationException("method2() is not supported here.");
    }
}

Here while we do implement all methods, we throw a runtime exception should a caller try to access method2() .

Answer 2

You can do this by providing a default method implementation for the interface1 method in the interface itself.

interface Interface {
    default void interface1() {
        System.out.println("interface1");
    }

    void interface2();
}

class Clazz implements Interface {
    @Override
    public void interface2() {
        System.out.println("interface2");
    }
}

Answer 3

Depends how you define 'remove one method'.

If you have interface

interface Interface{
    void interface1();
    void interface2();
}

And for example two subclasses that extend it:

 class Class1 implementes Interface {
     @Override
     public void interface1(){ ... }
     @Override
     public void interface2(){ ... }
 }
 class Class2 implementes Interface {
     @Override
     public void interface1(){ ... }
     @Override
     public void interface2(){ ... }
 }

Then there are two scenarios:

1. You don't want to implement for example interface1() method in Class2:
2. You don't want to have interface1() method in Class2

In case of 1. as Robby Cornelissen mentioned, you can simply provide default implementation in Interface:

default void interface1() { /*do default thing*/ }

In case of 2. you need to remove the interface1() method from the Interface.

You can do that by simple moving definition of method interface1() to Class1 (and any other sublass that needs to have it). but that is not really generic approach.

Best is to extract for example Interface1 with method interface1() and use that interface in classes that need to have that method. You will end up with this situation:

interface Interface{
    void interface2();
}
interface Interface1{
    void interface2();
}

And for example two subclasses that extend it:

 class Class1 implementes Interface, Interface1 {
     @Override
     public void interface1(){ ... }
     @Override
     public void interface2(){ ... }
 }
 class Class2 implementes Interface {
     @Override
     public void interface2(){ ... }
 }