How to get a specific Map.Entry<K, V> for a specific key?

Question

I'm implementing a NavigableMap-implementing LinkedHashMap in Java. (There don't seem to be many (any?) reasons why LinkedHashMap doesn't implement NavigableMap already, but I digress...)

I've written lowerKey(), lowerEntry(), higherKey(), and higherEntry() by iterating the entrySet(). I don't see any way in these cases to avoid iterating the entire entrySet().

For floorKey(), floorEntry(), ceilingKey(), and ceilingEntry(), in the case that the key exists, I'd like to avoid the expense of iterating the entrySet(), considering that I can already get the value with plain-old get().

Is there a way to get the Map.Entry for a particular key, rather than just the value? Thanks.

Answer 1

@Sweeper's comment on his answer got me thinking. The solution I came up with was to maintain a Map from Key to Entry inside my class. That way I have a way of having O(1) access to the entrySet. Like so:

Map<K, Map.Entry<K, V>> entryMap = new HashMap<>();
for(final currentEntry : entrySet())
{
    entryMap.put(currentEntry.getKey(), currentEntry);
}

I just need to update this Map every time an operation runs which changes the keySet. I only need to update the one entry in this Map that would be affected. That sounds like it wouldn't be very expensive.