code: private boolean isEqual(Object a, Object b) {
  
          if (a == null) {
              return (b == null);
          }
          if (b == null) {
              return false;
          }
          return a.equals(b);
      }
docs: Checks if two objects are either both null, or equal.<p>
  
  @param a the first object to check
  @param b the second object to check
  @return true if the two object are either both null, or equal