Comparators.comparing overloads

Richard Warburton richard.warburton at
Sun Jul 21 14:16:26 PDT 2013


We only mangle the name for return types, not argument types.

Thanks for the prompt reply.

Things still seem a little messy in this situation though.  Perhaps I've
missed something but we're talking about needing a cast for
any keyExtractor function that returns a number.  That seems to be a fairly
common scenario for a keyExtractor.  Suppose I want to sort Strings by
length, and I want to write:

Comparator<String> comparator = comparing(String::length);

I'll get an error telling me that the "reference to comparing is
ambiguous".  Now in fact I can't even hint to the compiler using a return
type cast as with the following snippet:

Comparator<String> comparator = comparing(str -> (int) str.length());

I presume this is because a cast to int can auto-box to Integer which
subtypes Object, so its still ambiguous between Function and ToIntFunction.
 Again, perhaps I've missed something here, but the way to get around this
issue is by providing an explicit type for the keyExtractor function:

ToIntFunction<String> lengthOfString = String::length;
Comparator<String> comparator = comparing(lengthOfString);

Which really does seem less elegant to me than having overloads with
mangled names. As I say this isn't a weird corner case - numbers are an
obvious thing to use as a comparator key.


  Dr. Richard Warburton
  @RichardWarburto <>

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