The Comparable and Comparator interfaces in Java

 The Comparable and Comparator interfaces in Java are both used for sorting objects, but they serve different purposes and provide different mechanisms for comparison.

Comparable Interface:

1. Purpose:

   - The Comparable interface is used to define the natural ordering of objects. It enables objects of a class to be compared to one another based on a predefined criterion.

   - Objects that implement Comparable can be sorted automatically based on their natural ordering.

2. Method:

   - The Comparable interface contains a single method, `compareTo(Object obj)`, which compares the current object with another object of the same type.

   - The `compareTo` method returns a negative integer, zero, or a positive integer depending on whether the current object is less than, equal to, or greater than the specified object.

3. Usage:

   - Comparable is typically implemented by the class of the objects being sorted.

   - It defines the default sorting behavior for objects of that class.

Comparator Interface:

1. Purpose:

   - The Comparator interface is used to define custom ordering of objects. It provides a way to compare objects based on criteria other than their natural ordering.

   - It allows for multiple different ways to compare objects, providing more flexibility in sorting.

2. Method:

   - The Comparator interface contains a single method, `compare(Object obj1, Object obj2)`, which compares two objects of the same type.

   - The `compare` method returns a negative integer, zero, or a positive integer depending on whether the first object is less than, equal to, or greater than the second object.

3. Usage:

   - Comparator is typically implemented as a separate class or as a lambda expression.

   - It allows for custom sorting logic to be defined independently of the class of the objects being sorted.

Key Differences:

1. Implementation:

   - Comparable is implemented by the class of the objects being sorted, while Comparator is implemented as a separate class or as a lambda expression.

2. Default vs. Custom Ordering:

   - Comparable defines the default natural ordering for objects, whereas Comparator allows for custom ordering based on specified criteria.

3. Flexibility:

   - Comparable provides a single way to compare objects based on their natural ordering, while Comparator allows for multiple different comparison criteria to be defined.

In summary, Comparable is used for defining the natural ordering of objects within a class, while Comparator provides a way to define custom ordering of objects based on specific criteria, offering more flexibility in sorting.