CODEWITHSUNDEEP
java
EdgeCase
EdgeCase

Reputation: 4827

Why Does My Generic Method Require a Cast?

I have a service layer method that I want to expose that should return an instance of an object that extends CMSContent (e.g. Delivery Time, Price). However, in method getCMSContent, the compiler is insisting that I do a cast to T. Is this cast below acceptable, or am I defeating the purpose of generics?

I compile with "-Xlint:unchecked" and receive no warnings, and it functions as I expect.

    public <T extends CMSContent> T getCMSContent(String cmsKey, Class<T> clazz) {
        T cmsInstance = (T) CMSObjectCache.getCachedCMSObject(cmsKey, clazz);
        return cmsInstance;
    }

This is the entire method of getCachedCMSObject

public static <T> T getCachedCMSObject(String objectKey, Class<T> cls) {
    init();
    CMSObject cmsObject = cmsObjectCache.get(objectKey);
    if (cmsObject != null) {
        return cmsObject.getCMSObject(cls);
    }
    return null;
}

Upvotes: 1

Views: 111

Answers (1)

Garrett Hall
Garrett Hall

Reputation: 30022

Since the the signature of getCachedCMSObject is:

T getCachedCMSObject(String cmsKey, Class<T> clazz)

your cast is to T is unnecessary although you may want to throw an exception rather than return a null.

Upvotes: 1

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