Javadocs and jdk mismatch on NavigableSet/Map?

The NavigableSet API docs state that methods headSet,tailSet(E),headSet(E) and subSet(E, E) return a NavigableSet.

In Eclipse,开发者_高级运维 I get a type mismatch error, although I use the 1.6_20 jdk and have my compiler compliance set to 1.6, so I have to "downgrade" the return value to SortedSet.

Am I missing something?

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You may have misread the javadoc. There two headSet methods, one returns SortedSet and the other returns NavigableSet. The same for the other methods you mentioned.