Assuming that BIGGEST was declared after BIG in the enumeration. The ordinal value in an enumeration is implicitly tied to the declaration order, by default the first value is assigned value 0, the second value 1 and so on.
So if yo declared the enumeration like this, things will work:
Implementing Comparable doesn't mean that you can use < or >. You can only use those with numeric values.
It only means that there's a compareTo() method. Try this:
This method will return an int that is smaller than, equal to or bigger than 0, depending on which value is "bigger". In the case of enum values the "size" depends on the order of the enum value definitions.