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javagenericsmethodstypesafegeneric-method

Difference between generic super class and super class type

I can't understand the difference between the two code snippets below. Can someone help me with a simple explanation?

First of all, I have to say that I have a lot of classes that extend a super class named BaseEntity, so what are the differences, benefits and drawbacks of the following snippets?

// 1
public <T extends BaseEntity> T getName(T t) {
    return t;
}

// 2
public BaseEntity getName(BaseEntity t) {
    return t;
}
Solution

  • The first snippet is more flexible as it preserves the actual type of T. Suppose you have a subclass:

    class SubEntity extends BaseEntity {}

    In the first case you can write:

    SubEntity result = getName(new SubEntity());

    But in the second case you will need a cast:

    SubEntity result = (SubEntity)getName(new SubEntity());