inheriting interfaces

[P. Ingle]

Hello,

Does a subclass inherit the interfaces that base classes implements?

In particular, if I have a base class implementing 'Serializable', does subclass automatically implement it?

Thanks,
P Ingle

[Stan James]

Hi, welcome to the ranch! In this forum we often encourage you to answer your own questions a little bit at a time. For this one, why not just try it? Make an interface I with one method, a class A that implements I and a class B that extends A. Then see if ( B instanceOf I ).

Also try saying "A implements I" but don't actually code the required method in A. What does the compiler tell you then?

Don't be discouraged by this answering a question with a question. Or two. We really want you to have the joy of working things out. They'll stick in your head much better that way! Let us know what you find and whether it makes sense.

[P. Ingle]

Thanks for the suggestion. My qusetion was related to serializable (or similar) interface that does not have any method of it's own. I have BaseClass inplementing Serializable and SubClass extending BaseClass. So how do I make sure that SubClass really is serializable.

I took your suggestion and tried with following classes:


public interface TempI {
public void tempMethod();

}

<B>
// I made BaseClass abstract so compiler did not complain even if I didn't
// have implementaion of tempMethod()
</B>

public abstract class BaseClass implements TempI {

}

<B>
//If I remove tempMethod() from SubClass, compiler complains
// so I know for sure that it is indeed implementing
// interface TempI
</B>

public class SubClass extends BaseClass {


/* (non-Javadoc)
* @see testTemp.TempI#tempMethod()
*/
public void tempMethod() {
// TODO Auto-generated method stub

}

Thanks,
P Ingle

[Stuart Gray]

Thanks for the suggestion. My qusetion was related to serializable (or similar) interface that does not have any method of it's own. I have BaseClass inplementing Serializable and SubClass extending BaseClass. So how do I make sure that SubClass really is serializable.

Serializable is a 'tag' interface; it doesn't contain any methods, it is just used to indicate to the system that this class should be Serializable. However it behaves in exactly the same way as other interfaces, so your subclass will indeed be Serializable if the base class is.

[marc weber]

import java.io.*;
 
class MyBase implements Serializable {}
 
class MySub extends MyBase {}
 
public class TestSer {
  public static void main(String[] args) {
    MySub m = new MySub();
    boolean s = m instanceof Serializable;
    System.out.println("MySub Serializable: " + s);
  }
}

[P. Ingle]

Originally posted by marc weber:

import java.io.*;
 
class MyBase implements Serializable {}
 
class MySub extends MyBase {}
 
public class TestSer {
  public static void main(String[] args) {
    MySub m = new MySub();
    boolean s = m instanceof Serializable;
    System.out.println("MySub Serializable: " + s);
  }
}

Cool, it made it explicitly prooved to me that the subclass does implement serializable - Thanks,
P Ingle