Collections in Guava

Google Guava is an open source library which provides lots of useful utility to Java programmer,  one of them is easy way to find the difference between two maps.
MapDifference of two Maps

public void getMapDiff() {
    Map<Integer,Integer> leftMap = ImmutableMap.of(1, 1, 2, 2, 4, 40);
    Map<Integer,Integer> rightMap = ImmutableMap.<Integer,Integer> builder()
        .put(2, 2).put(3, 3).put(4, 41).build();
    MapDifference<Integer,Integer> diff = Maps.difference(leftMap, rightMap);
    
    // output: entriesInCommon:{2=2}
    System.out.println("entriesInCommon:" + diff.entriesInCommon());
    // output: entriesOnlyOnLeft:{1=1}
    System.out.println("entriesOnlyOnLeft:" + diff.entriesOnlyOnLeft());
    // output: entriesOnlyOnRight:{3=3}
    System.out.println("entriesOnlyOnRight:" + diff.entriesOnlyOnRight());
    
    Map<Integer,ValueDifference<Integer>> entriesDiffering = diff
        .entriesDiffering();
    // output: entriesDiffering: {4=(40, 41)}
    System.out.println("entriesDiffering: " + entriesDiffering);
  }