CODEWITHSUNDEEP
javagenerics
user2269707
user2269707

Reputation:

how to bypass java generics type checking

I got a interface like this:

public T evaluate(float fraction, T startValue, T endValue);

the other code will treat every T type as an Object, and finally I'll get the return value, which is an Object class too.

What I want is to pass startValue and endValue as integer, but return a totally different instance (not an Integer). I'll force cast the return value to what I supposed.

What I've done is to replace the T with object, like this:

public Object evaluate(float fraction, Object startValue, Object endValue)

but this failed, I thought if the interface defined like ? extends T will work, but it's not. (Am I right?)

So is there any way I can bypass the generics type check?

Upvotes: 0

Views: 613

Answers (2)

Furetur
Furetur

Reputation: 471

I wrote this answer a long time ago when I didn't know much. Please consider the other answers.

I suppose you have an interface like interface Name<T>{}. Why not just let T be Integer and then cast what is returned to whatever you want. (if I wanted to get a string):

//interfaceInstance is Name<Integer>
//fraction is float, startValue and endValue are Integer
String value = String.valueOf(interfaceInstance.evaluate(fraction, startValue endValue))

Upvotes: 0

Maurice Perry
Maurice Perry

Reputation: 9658

Assuming your interface has a T generic parameter, add a second type, say R:

interface MyInterface<T,R> {
    public R evaluate(float fraction, T startValue, T endValue);
}

Upvotes: 4

Related Questions