Comparable Interface

Objects that have an ordering are compared using the compareTo() method.

6. Rules for compareTo()



Rules for compareTo()

With all objects, compareTo() works the way number comparisons work in ordinary arithmetic. Here are a few rules. Most of these are sensible if you think about numbers. Say that AB, and C are Integers.


If A.compareTo(B) > 0 and B.compareTo(C) > 0 then A.compareTo(C) > 0.


If A.compareTo(B) == 0 then A.compareTo(Z) and B.compareTo(Z) gives the same result, no matter what Z is.


The classes that come with Java follow these rules. If you write a class that implements Comparable, you need to follow these rules. This is not hard to do because most sensible compareTo() methods will do this naturally.

Question 6:

Say that X.compareTo(Y)==0.

Is it then true that X.equals(Y)?