Generics: Inheriting from an abstract class that implements an interface

Question

I have the following interface:

public interface SingleRecordInterface<T> {     public void insert(T object); } 

I have the abstract class below (that does not mention the method insert):

public abstract class AbstractEntry implements SingleRecordInterface<AbstractEntryBean> { } 

I have the concrete class:

public class SpecificEntry extends AbstractEntry {     public void insert(SpecificEntryBean entry) {         // stuff     } } 

Finally, SpecificEntryBean is defined as:

public class SpecificEntryBean extends AbstractEntryBean { } 

I have the following error:

The type SpecificEntry must implement the inherited abstract method SingleRecordInterface.insert(AbstractEntryBean)

I don't understand the reason for this error, given that SpecificEntryBean extends AbstractEntryBean. How do I fix this error?

Answer 1

You need to make your abstract class generic as well:

public abstract class AbstractEntry<T extends AbstractEntryBean> implements SingleRecordInterface<T> { } 

Then for your concrete class:

public class SpecificEntry extends AbstractEntry<SpecificEntryBean> { } 

Answer 2

Change to the following:

public abstract class AbstractEntry<EB extends AbstractEntryBean> implements SingleRecordInterface<EB> { } 

and

public class SpecificEntry extends AbstractEntry<SpecificEntryBean> {     public void insert(SpecificEntryBean entry) {         // stuff     } }