In Java, Comparable and Comparator are two interfaces that can be used to define the ordering of objects.
Comparable is an interface that defines a natural ordering for objects of a class. It is implemented by the class itself, and the compareTo method is used to compare two objects of the same class. For example, the String class implements the Comparable interface, so you can use the compareTo method to compare two String objects lexicographically.
On the other hand, Comparator is an interface that defines a custom ordering for objects of a class. It is a separate class that implements the Comparator interface, and the compare method is used to compare two objects of the class. The Comparator interface allows you to define multiple orderings for the same class, which can be useful in different scenarios. For example, you could define a Comparator for the String class that sorts strings by length rather than lexicographically.
Here are some guidelines for when to use Comparable and Comparator:
Use Comparable when the class has a natural ordering that should be used in all cases, and you don’t need to support multiple orderings. For example, the String class has a natural ordering based on lexicographic order, so it implements the Comparable interface.
Use Comparator when you need to define a custom ordering for a class, or when you need to support multiple orderings. For example, you might define a Comparator for the Person class that sorts people by age, and another Comparator that sorts people by name.
If you want to sort a collection of objects using a custom order, use the Collections.sort method that takes a Comparator argument. This method sorts the collection according to the ordering defined by the Comparator.
In summary, Comparable and Comparator are both user interfaces for defining the ordering of objects in Java. Comparable is used when the class has a natural ordering, while Comparator is used when you need to define a custom ordering or support multiple orderings.
You may also like:
Is there concurrent version for TreeMap and TreeSet in Java Collections Framework?
What are fail-fast and fail-safe Iterator?
What is difference between Iterator and LisIterator?
Why Prime Numbers are considered in writing certain algorithms like hashcode()?