MapDiff.java

import java.util.*;

class MapDiff {
    public static void main(String[] args) {
        Map<String, Integer> m1 = new HashMap<String, Integer>();
        m1.put("a", 1);
        m1.put("b", 2);
        m1.put("c", 3);

        Map<String, Integer> m2 = new HashMap<String, Integer>();
        m2.put("a", 1);
        m2.put("b", 3);
        m2.put("c", 3);

        Set<Map.Entry<String, Integer>> defaultEntries = m1.entrySet();
        Set<Map.Entry<String, Integer>> overridenEntries = m2.entrySet();

        overridenEntries.removeAll(defaultEntries);
        System.out.println(m2);
        // "{b=3}"
    }
}