Upendra 
Comparable vs Comparator
Comparable
Comparable interface has a single method compareTo() which is used to compare the value of an object with the one supplied in the method. Comparable interface defines the natural or default ordering of the objects of a class. On defining the compareTo() method in the class, we need to make sure that the return value can be:
- Negative: Returns negative if the object which is to be compared is less than the supplied object value.
- Positive: Returns positive if the object which is to be compared is greater than the supplied object value.
- Zero: Returns zero, if the object which is compared is equal to the supplied object value.
Comparator
Comparator interface is used for the scenarios when we don’t want to use the natural ordering and want the ordering/ sorting of elements according to the specific requirements. As we cannot make any changes to the compareTo() method of Comparable interface, the Comparator interface provides a method compare() which is used to sort the objects of collection. It takes 2 arguments in the method and return value can be:
- Negative: Returns a negative value if the value of the first argument is less than the value of the second argument.
- Positive: Returns a positive value if the value of the first argument is greater than the value of the second argument.
- Zero: Returns a zero value if the value of the first argument is equal to the value of the second argument.
Conclusion
| Comparable | Comparator |
|---|---|
| Comparable affects the original class, i.e., the actual class is modified. | Comparator doesn’t affect the original class, i.e., the actual class is not modified. |
| Comparable provides compareTo() method to sort elements. | Comparator provides compare() method to sort elements. |
| We can sort the list elements of Comparable type by Collections.sort(List) method. | We can sort the list elements of Comparator type by Collections.sort(List, Comparator) method. |
| Can sort the elements of collection on the basis of the single element | Can sort on the basis of multiple elements of the collections at a time |
Links
https://www.educba.com/comparable-vs-comparator/
https://www.baeldung.com/java-comparator-comparable
https://www.javatpoint.com/difference-between-comparable-and-comparator
https://dev.to/micosmin/understanding-comparable-and-comparator-3l0i
https://www.javaworld.com/article/3323403/java-challengers-5-sorting-with-comparable-and-comparator-in-java.html