CODEWITHSUNDEEP
javagenerics
ceving
ceving

Reputation: 23814

Type arguments in Java

Is there any difference between the following two declarations?

public<C extends Condition<E>> List<E> search (C condition)

public List<E> search (Condition<E> condition)

One difference is obvious: in the first case C can be used in the body of search. But assumed that C would not be used in the body of search: is there still any difference?

Upvotes: 1

Views: 113

Answers (1)

Paul Bellora
Paul Bellora

Reputation: 55213

No, there's no useful difference. The distinction could be simplified to the following.

<T> void m(T object)

void m(Object object)

Although with the first one could call this.<String>m(42) and it wouldn't compile - but there's no value to that.

The value of a generic method comes when there is some relationship expressed by its type parameters, for example:

<T> T giveItBackToMe(T object) {
    return object;
}

...

String s = giveItBackToMe("asdf");
Integer i = giveItBackToMe(42);

Or:

<T> void listCopy(List<T> from, List<? super T> to) {
    to.addAll(from);
}

...

List<Integer> ints = Arrays.asList(1, 2, 3);
List<Number> nums = new ArrayList<>();
listCopy(ints, nums);

Upvotes: 1

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