CODEWITHSUNDEEP
javagenericscasting
rage
rage

Reputation: 69

Java: Casting a List<?> without warning

Assume we have following example code.

First Class:

public class Template<T> {

    private final T val;

    public Template(T val) {
        this.val = val;
    }

    public T getVal() {
        return val;
    }
}

Second class: 

import java.util.ArrayList;
import java.util.List;

public class App {

    public static void main(String[] args) {

        List<?> templates = new ArrayList<Template<?>>();

        // How can I cast this without warning?
        List<Template<?>> castedTemplates = (List<Template<?>>)templates;

        // further code...
    }
}

So, my question is: How can I do the cast without warning and without @SuppressWarnings("unchecked")?

Upvotes: 1

Views: 2054

Answers (2)

peter.petrov
peter.petrov

Reputation: 39477

You cannot do it.

This is the point - the compiler has to generate those warnings so that they warn you that you're doing something not quite by the book.

And the @SuppressWarnings("unchecked") is supposed to suppress them (if that's what you explicitly want).

I know it sounds too trivial as an answer but it's true.

Upvotes: 1

Robby Cornelissen
Robby Cornelissen

Reputation: 97282

Why would you if you can just define it as List<Template<?>> templates = new ArrayList<Template<?>>();?

Upvotes: 2

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