code: private boolean isEqual(Object o1, Object o2) {
  		return o1 == null ? o2 == null : o1.equals(o2);
  	}
docs: Checks whether 2 objects are equal. Null-safe, 2 null objects are considered equal.
  
  @param o1
  first object to compare
  @param o2
  second object to compare
  @return true if object are equal, false otherwise