Best practice for reducing common variables in type hierarchies?

Question

I am wondering if java generics can be made more readable and / or easier to use with a type hierarchy and many common variables. While I am not familiar with Java generics. What can be done in the following example:

Suppose I need the following class ...

abstract class BaseClass<T> {}

... to work with lists of the next class ...

class Foo<T1, T2> {}

... and further provoke an iterator over such instances.

So, I would do the following:

class ImplClass<T1, T2> extends BaseClass<List<Foo<T1, T2>>> implements Iterator<Foo<T1, T2>> {}

Assume also that there is an interface with a base class:

interface Manipulator<T, B extends BaseClass<T>> {
  void doSomething(B baseClassInstance);
}

Thus, when writing classes that implement this interface for ImplClass, I will always need to write all this common signature, right? So something like:

class ManipulatorA<T1, T2> implements Manipulator<List<Foo<T1, T2>>, ImplClass<T1, T2>> {
  @Override
  void doSomething(ImplClass<T1, T2> baseClassInstance) {...}
}
class ManipulatorB<T1, T2> implements Manipulator<List<Foo<T1, T2>>, ImplClass<T1, T2>> {
  @Override
  void doSomething(ImplClass<T1, T2> baseClassInstance) {...}
}

EMPTY-, , :

interface ImplManipulator<T1, T2> extends Manipulator<List<Foo<T1, T2>>, ImplClass<T1, T2>>{
  // actually empty
}

:

class ManipulatorA<T1, T2> implements ImplManipulator<T1, T2> {
  @Override
  void doSomething(ImplClass<T1, T2> baseClassInstance) {...}
}
class ManipulatorB<T1, T2> implements ImplManipulator<T1, T2> {
  @Override
  void doSomething(ImplClass<T1, T2> baseClassInstance) {...}
}

. . , ?

Answer 1

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