Java: Maximum value in TreeMap

Question

If I have a TreeMap:

TreeMap<String, Integer> map = new TreeMap<String, Integer>();

I want to print out the String with the highest value. I have seen other questions about sorting, but I am wondering If there is any smooth way to get the maximum value in the map?

score 1 · Answer 1 · answered Oct 28 '15 at 20:06

1

No, for that you'd need to switch your key and value. It's the keys that are sorted.

answered Oct 28 '15 at 20:06

Kayaman

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I was thinking the same thing, but will a tree reliably sort a primitive wrapper class? – Patrick J Abare II Oct 28 '15 at 20:07
2

Yes, they all implement `compareTo()` properly. – Kayaman Oct 28 '15 at 20:08

Paul Boddington · Accepted Answer · 2015-10-28T20:26:50.397

1

Using Java 8, a one-liner for getting a key with the highest value is:

String s = map.entrySet()
              .stream()
              .max(Map.Entry::comparingByValue)
              .map(Map.Entry::getKey)
              .orElse(null);

s will be null if the map is empty.

edited Oct 28 '15 at 20:26

answered Oct 28 '15 at 20:17

Paul Boddington

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score 0 · Answer 3 · answered Oct 28 '15 at 20:13

TreeMap<String, Integer> map = new TreeMap<String, Integer>();

becomes:

Map<Integer, Collection<String>> map = new TreeMap<>();

Assuming you want all highest value strings, else you only want any such string you can use this construct:

Map<Integer, String> map = new TreeMap<>();

Java: Maximum value in TreeMap

3 Answers3