It's very convenient to type a code, using methods which are to be defined in a moment (but there're not defined yet), then have a quick refactor option to let IDE generate the method for you using arguments that we passed to the method and (optionally) the return argument that we use from it.

Example: Type a code like this:

Type1 var1;
Type2 var2;
Type3 var3 = process(var1, var2);

Then go to 3rd line, hit Alt+Enter and we should have option like: "Generate private method process() from this use case" (or something like that).

This would cause the new private method to be generated in the class:

Type3 ClassName::process(Type1 var1, Type2 var2)
{
    // TODO implement
}