Question

i have 2 different classes. One is a generic valueHolder, that can contain anything that extends number.

class ValueHolder<T extends number>{
    private T currentValue;

   //more functions, database logic, etc...
}

the other class is more complex, and has a “targetValue”. Also its parameterized like this:

class MoreComplexClass<T extends ValueHolder<?>>
    private T valueHolder;
    private XXX requiredValue;

    //a lot more functions.
}

Is it “possible” to use the Type of the valueHolder for the requiredValue of the MoreComplexClass?
What i am trying to achieve is: Beeing able to compare currentValue and requiredValue with > == < Operators without casting and without loosing Typesafety. (Maybe i’m also thinking way to complex to achiee this)

Answer 1

the answer is YES, you can declare the complex class this way:

class MoreComplexClass<N extends Number, T extends ValueHolder<N>>
    private T valueHolder;
    private N requiredValue;

    //a lot more functions.
}

but since you are using the Number class, you won’t be able to use those operators, you’ll need to use one of the XXXvalue() methods (i.e.: doubleValue(), longValue()) from the Number class to able to use those operators.