Generally, this is how you can filter a map by its values:

static <K, V> Map<K, V> filterByValue(Map<K, V> map, Predicate<V> predicate) {
    return map.entrySet()
            .stream()
            .filter(entry -> predicate.test(entry.getValue()))
            .collect(Collectors.toMap(Entry::getKey, Entry::getValue));
}

Call it like this:

Map<String, Integer> originalMap = new HashMap<>();
originalMap.put("One", 1);
originalMap.put("Two", 2);
originalMap.put("Three", 3);

Map<String, Integer> filteredMap = filterByValue(originalMap, value -> value == 2);

Map<String, Integer> expectedMap = new HashMap<>();
expectedMap.put("Two", 2);

assertEquals(expectedMap, filteredMap);