Java – Why would an interface override methods of the interface(s) it extends in Java 7

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I was looking at Map and SortedMap documentation from Java 7 and I have realized that SortedMap, which extends Map overrides entrySet(), keySet() and values().

AFAIK, interfaces cannot implement a method in Java prior to Java 8. So what was the reason for overriding these methods?

Best Answer

It looks as though the methods were overridden solely so that different documentation could be provided.

For all three methods, the only difference in documentation is that the SortedMap version adds "The set's iterator returns the entries in ascending key order." to the main description and "sorted in ascending key order" to the return value description.

P.S. The obvious follow-up question is why weren't these three method signatures simply changed to return SortedSet instead of Set. Unfortunately I can't come up with a reason for this, as the Java language seems to allow this sort of change, and the additional methods on SortedSet seem trivial to implement.

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