When should a class be Comparable and/or Comparator?

Question

I have seen classes which implement both Comparable and Comparator. What does this mean? Why would I use one over the other?

Answer 1

Comparable is for objects with a natural ordering. The object itself knows how it is to be ordered.
Comparator is for objects without a natural ordering or when you wish to use a different ordering.

Answer 2

Comparable is for providing a default ordering on data objects, for example if the data objects have a natural order.

A Comparator represents the ordering itself for a specific use.

Answer 3

The text below comes from Comparator vs Comparable

Comparable

A comparable object is capable of comparing itself with another object. The class itself must implements the java.lang.Comparable interface in order to be able to compare its instances.

Comparator

A comparator object is capable of comparing two different objects. The class is not comparing its instances, but some other class’s instances. This comparator class must implement the java.util.Comparator interface.

Answer 4

Implementing Comparable means "I can compare myself with another object." This is typically useful when there's a single natural default comparison.

Implementing Comparator means "I can compare two other objects." This is typically useful when there are multiple ways of comparing two instances of a type - e.g. you could compare people by age, name etc.

Answer 5

Difference between Comparator and Comparable interfaces

Comparable is used to compare itself by using with another object.

Comparator is used to compare two datatypes are objects.