CODEWITHSUNDEEP
javagenericsoverloading
Ignasi
Ignasi

Reputation: 6185

Java overloading methods with generic and a collection of a generic

Having an interface with these two methods:

void add(T result);
void add(List<T> result);

I was expecting Java on runtime will call the appropriated method:

final U result = getResult();
myInterface.add(result);

If U is a list I thought second method would be called, but always the first one is called. Why this behavior? What should be the correct way to achieve that?

Upvotes: 3

Views: 455

Answers (1)

Kayaman
Kayaman

Reputation: 73568

It depends on the compile-time type of U. If U is unbounded, the compiler can't determine whether it's a List or a String or your aunt Hilda. So the "ungenericized" code becomes:

final Object result = getResult();
myInterface.add(result);

However, if U is actually <U extends List<?>>, the compiler can narrow down the possibilities (with your help) and the "ungenericized" code becomes:

final List result = getResult();
myInterface.add(result);

giving you the expected overloaded method call.

Upvotes: 3

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