Tested with below sample snippet, tried with MapUtils, and Java8 Stream feature. It worked with both cases.
public static void main(String[] args) {
Map<String, String> test = new HashMap<String, String>();
test.put("a", "1");
test.put("d", "1");
test.put("b", "2");
test.put("c", "3");
test.put("d", "4");
test.put("d", "41");
System.out.println(test);
Map<String, String> test1 = MapUtils.invertMap(test);
System.out.println(test1);
Map<String, String> mapInversed =
test.entrySet()
.stream()
.collect(Collectors.toMap(Map.Entry::getValue, Map.Entry::getKey));
System.out.println(mapInversed);
}
Output:
{a=1, b=2, c=3, d=41}
{1=a, 2=b, 3=c, 41=d}
{1=a, 2=b, 3=c, 41=d}