Annotate parameters of Ordering methods as @Nullable

[GoogleCodeExporter]

Some methods of Ordering (e.g. compare, min, max) can sometimes be passed 
null arguments, e.g. if the ordering was returned by Ordering.nullsFirst() 
or Ordering.nullsLast().

The parameters could be annotated @Nullable, but maybe it would make more 
sense to add a public intermediate class (returned by nullsFirst() and 
nullsLast()) that has @Nullable parameters, overriding the (sensible) 
default of @NonNull for the parameters of Comparator.compare.

e.g.

public abstract class Ordering<T> {

  public NullableOrdering nullsFirst() {
    return new NullsFirstOrdering(this);
  }

  private static class NullsFirstOrdering<T> extends NullableOrdering<T> {
    // ...
  }

}

public abstract class NullableOrdering<T> extends Ordering<T> {

  public abstract int compare(@Nullable T a, @Nullable T b);

  public abstract T min(@Nullable T a, @Nullable T b);

  // ...
}

Original issue reported on code.google.com by fin...@gmail.com on 8 Apr 2010 at 9:57

[GoogleCodeExporter]

Aigh.  I believe that @Nullable status is not going to be nearly enough 
justification 
to create a new public type.  So we have to just add @Nullable to these 
Ordering 
methods. I believe @Nullable is only supposed to mean "might accept null", as 
opposed 
to "definitely rejects null".

Original comment by kevinb@google.com on 9 Apr 2010 at 7:12

[GoogleCodeExporter]

Original comment by kevinb@google.com on 30 Jul 2010 at 3:50

• Added labels: Milestone-Release07

[GoogleCodeExporter]

thanks!

Original comment by kevinb@google.com on 14 Sep 2010 at 8:50

• Changed state: Fixed

[GoogleCodeExporter]

This issue has been migrated to GitHub.

It can be found at https://github.com/google/guava/issues/<id>

Original comment by cgdecker@google.com on 1 Nov 2014 at 4:15

• Added labels: MigratedToGitHub

[GoogleCodeExporter]

Original comment by cgdecker@google.com on 3 Nov 2014 at 9:10

• Added labels: Restrict-AddIssueComment-Commit