How to print keys with duplicate values in a hashmap?

Question

I have a hashmap with some keys pointing to same values. I want to find all the values that are equal and print the corresponding keys.

This is the current code that I

Answer 1

Build a Map>, i.e. a Map>.

Example

Map map = new HashMap<>();
map.put("hello", "0123");
map.put("hola", "0123");
map.put("kosta", "0123");
map.put("da", "03");
map.put("notda", "013");
map.put("twins2", "01");
map.put("twins22", "01");

map.entrySet().stream()
   .collect(Collectors.groupingBy(Entry::getValue,
               Collectors.mapping(Entry::getKey, Collectors.toList())))
   .entrySet().stream()
   .filter(e -> e.getValue().size() > 1)
   .forEach(System.out::println);

Output

01=[twins22, twins2]
0123=[kosta, hello, hola]

Without the filter(), the result would be:

01=[twins22, twins2]
013=[notda]
03=[da]
0123=[kosta, hello, hola]