Class Test {
   private int a;
   private int b;
   public int getA() {
      return a;
   }
   public void setA(int a) {
      this.a = a;
   }
   public int getB() {
      return b;
   }
   public void setB(int b) {
      this.b = b;
   }
   public Map<String, int> constructChangeDataMap() {
      // check what values has been modified and construct the map
   }
}