CODEWITHSUNDEEP
javagenerics
ana
ana

Reputation: 41

Type safety: Unchecked cast from Object to T (Java)

I am making a HashMap with keys T and values Long, and my remove method (which is overrided from the AbstractCollection class) looks like this:

 public boolean remove(Object o) {
    if(denseBag.containsKey(o)){
        if(denseBag.get(o) == 1L){
            denseBag.remove(o);
        } else {
            Long removed = denseBag.get(o);
            T theO = (T) o;
            denseBag.replace(theO, removed, removed--); 
        }
    } else {
        return false;
    }

I am getting the message: "Type safety: Unchecked cast from Object to T". I just want to make sure that it will work OK. Thank you.

Upvotes: 3

Views: 7495

Answers (2)

Anonymous
Anonymous

Reputation: 86276

Your code will work correctly from all I can tell. If you can, I suggest you change the declaration of your method to

public boolean remove(T o)

With this you should not need the unchecked cast, which would make your code a little bit simpler. If you cannot and you believe us when we say your code is correct, use @SuppressWarnings("unchecked") as Alexey Soshin said. And consider factoring the cast out into a separate method castToT(Object obj) or what you wish to call it. The advantage of the tag is next time you get a friendly warning from your compiler or IDE, you know it’s not just an old one that you have chosen once to ignore.

Upvotes: 1

Alexey Soshin
Alexey Soshin

Reputation: 17721

It will. Java uses Object o signature in Collections for legacy reasons.
If that bothers you still, use @SuppressWarnings("unchecked").

You'll still have a lot of other troubles, though.

This will be ignored: removed--, use --removed

Upvotes: 7

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