Collections.emptyList() returns a List<Object>?

Question

I\'m having some trouble navigating Java\'s rule for inferring generic type parameters. Consider the following class, which has an optional list parameter:

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Answer 1

the emptyList method has this signature:

public static final  List emptyList()

That before the word List means that it infers the value of the generic parameter T from the type of variable the result is assigned to. So in this case:

List stringList = Collections.emptyList();

The return value is then referenced explicitly by a variable of type List, so the compiler can figure it out. In this case:

setList(Collections.emptyList());

There's no explicit return variable for the compiler to use to figure out the generic type, so it defaults to Object.