Difference between Comparable and Comparator?

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.

Usage-

There are two interfaces in Java to support these concepts, and each of these has one method to be implemented by user.
Those are;

java.lang.Comparable: int compareTo(Object o1)
This method compares this object with o1 object. Returned int value has the following meanings.
positive – this object is greater than o1
zero – this object equals to o1
negative – this object is less than o1

java.util.Comparator: int compare(Object o1, Objecto2)
This method compares o1 and o2 objects. Returned int value has the following meanings.
positive – o1 is greater than o2
zero – o1 equals to o2
negative – o1 is less than o2

java.util.Collections.sort(List) and java.util.Arrays.sort(Object[]) methods can be used to sort using natural ordering of objects.
java.util.Collections.sort(List, Comparator) and java.util.Arrays.sort(Object[], Comparator) methods can be used if a Comparator is available for comparison.