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.

If an Employee class is present and its objects are added in an arrayList. Now I want the list to be sorted on the basis of the employeeID of Employee class. What are the steps?

Ans) 1) Implement Comparable interface for the Employee class and override the compareTo(Object obj) method in which compare the employeeID

2) Now call Collections.sort() method and pass list as an argument.
Now consider that Employee class is a jar file.
1) Since Comparable interface cannot be implemented, create Comparator and override the compare(Object obj, Object obj1) method .
2) Call Collections.sort() on the list and pass comparator as an argument.