CODEWITHSUNDEEP
javagenerics
aliteralmind
aliteralmind

Reputation: 20163

Just passing Java generic type through, but still getting not-within-its-bound error

I have this class:

public abstract class SuperClass<
   CONE extends ClassOne,
   OBJ,
   VOBJ extends ValidateValue<OBJ>>

which I'm trying to extend with this:

public class SubClass<CONE,VOBJ>
   extends SuperClass<CONE,Object,VOBJ>  {

but am getting these two errors.

type parameter CONE is not within its bound
public class SubClass<CONE,VOBJ> extends SuperClass<CONE,Object,VOBJ>  {
type parameter VOBJ is not within its bound
public class SubClass<CONE,VOBJ> extends SuperClass<CONE,Object,VOBJ>  {

If I change SubClass to this:

public class SubClass
   extends SuperClass<ClassOne,Object,ValidateValue<Object>>  {

It compiles fine.

This makes no sense to me, as I'm simply passing CONE and VOBJ up the chain.

I would appreciate some advice. This is puzzling me. Thank you.

Upvotes: 1

Views: 115

Answers (1)

Sotirios Delimanolis
Sotirios Delimanolis

Reputation: 279940

The type parameters declared in

public class SubClass<CONE,VOBJ>

ie. ONE and VOBJ don't have the bounds that SuperClass is expecting and therefore can't be used as type arguments for the parent class. It would need to be

public class SubClass<CONE extends ClassOne, VOBJ extends ValidateValue<Object>>>
   extends SuperClass<CONE, Object, VOBJ>  {
    ...
}

In your declaration that works

public class SubClass
   extends SuperClass<ClassOne,Object,ValidateValue<Object>>  {

you are passing type arguments that do match the bound. ClassOne matches T extends ClassOne and ValidateValue<Object> matches T extends ValidateValue<F> where F is Object.

Upvotes: 4

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