How to get key of a specific value in Map

Question

I am trying to find max value in a Map and get its corresponding key.

This is my maxMin =

{3=0.1518355013623417, 2=0.11815917264727849, 1=0.2467498197744391, 4=0.04812703040826949}

for(String keyset: maxMin.keySet()){
 double values = maxMin.get(keyset);
  if (values < min) {
       min = values;
  }
  if (values > max) {
       max = values;
  }
}

And I found the max but how toget corresponding key?

Relates to and possibly duplicates http://stackoverflow.com/questions/7146990/java-invert-map — Felix Frank, Jun 16 '14 at 08:50
You could use [Map#entrySet()](http://docs.oracle.com/javase/7/docs/api/java/util/Map.html#entrySet()) — John, Jun 16 '14 at 08:53

score 1 · Accepted Answer · answered Jun 16 '14 at 09:06

String minkey = null;
String maxkey = null;
for(String keyset: maxMin.keySet()){
  double values = maxMin.get(keyset);
  if (values < min) {
     min = values;
     minkey = keyset;
  }
  if (values > max) {
     max = values;
     maxkey = keyset;
  }
}

score 1 · Answer 2 · answered Jun 16 '14 at 09:08

This gives you the keys of the lowest and highest value:

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

map.put("lowest", 1);
map.put("5", 5);
map.put("highest", 10);
map.put("3", 3);

Map.Entry<String, Integer> min = null;
Map.Entry<String, Integer> max = null;

for (final Map.Entry<String, Integer> entry : map.entrySet()) {
    if ((null == min) && (null == max)) {
        min = entry;
        max = entry;
        continue;
    }

    if (entry.getValue() < min.getValue()) {
        min = entry;
    }

    if (entry.getValue() > max.getValue()) {
        max = entry;
    }
}

System.out.println("The key for the lowest value is: " + min.getKey());
System.out.println("The key for the highest value is: " + max.getKey());

score 0 · Answer 3 · answered Jun 16 '14 at 08:55

0

How about this:
int pos = 0;
int maxPos = 0;
for(String keyset: maxMin.keySet()){
 pos = pos + 1;
 double values = maxMin.get(keyset);
  if (values < min) {
       min = values;
  }
  if (values > max) {
       max = values;
       maxPos = pos;
  }
}

Set<Integer> keySet = maxMin.keySet();
List<Integer> keyList = new ArrayList<Integer>(keySet);
Integer key = keyList.get(maxPos);

answered Jun 16 '14 at 08:55

Programmer

325
5
18

-1 because: 2 accesses of the key set and an easily avoidable creation of an ArrayList. – laune Jun 16 '14 at 09:09
agree, I misunderstood the things, it was simple as you gave the solution :) – Programmer Jun 16 '14 at 09:11

score 0 · Answer 4 · answered Jun 16 '14 at 09:13

    for (Entry<String, Double> entry : maxMin.entrySet()) {
        if (entry.getValue() < min) {
            min = entry.getValue();
            minKey = entry.getKey();
        }
        if (entry.getValue() > max) {
            max = entry.getValue();
            maxKey = entry.getKey();
        }
    }

How to get key of a specific value in Map

4 Answers4