Comparable vs Comparator

Difference Between Comparable vs Comparator

In the following article, we will discuss the difference between Comparable vs Comparator. We first need to understand what are they and why are they used? Comparing the two values like 2 integers, 2 float values are easy in Java programming language using simple arithmetic operators but how can we compare the values of 2 objects like two Students, two Employees, etc. Comparing the objects of Collections in Java is a little bit difficult and can be done by simple arithmetic and comparison operators. For the comparison of Collection objects in Java, the Comparable and Comparator interfaces are used. Comparable and Comparator are the two interfaces present in 2 different Java packages to sort the collection of objects. Implementing these interfaces in the class, we can use the various methods of them.

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.

Head to Head Comparison between Comparable vs Comparator (Infographics)

Below are the top 6 differences between Comparable vs Comparator:

Key Difference between Comparable vs Comparator

Some of the key differences between the Comparable interface and Comparator interface are given below:

Comparator interface provides multiple ways of sorting the objects of Collections whereas Comparable interface provides only a single way of sorting the objects.
The comparable interface needs to be implemented by the class if it needs to use its methods whereas for Comparator nothing needs to be done in the original class.
Basically, Comparable is used for the objects with natural ordering, for example, in an Employee class, Employees need to be sorted on the basis of their Employee_id whereas in Comparator interface sorting needs to be done through a separate class.
Only a single object is passed as an argument in a Comparable interface whereas 2 arguments are passed in the Comparator interface which means a Comparable interface compares this reference with the value of the object specified in the method whereas in Comparator comparison is done with 2 different objects provided in an argument of the method.
Comparable is provided by default as it is present in java.lang package whereas Comparator is provided as a utility and is present in java. util package.
There is no need to use Arrays.sort(), Collections.sort() method if the class is implementing the Comparable interface as it automatically sorts the objects of Array and List using compareTo() method whereas it is not so in the case of Comparator interface.
Using Comparators allows us to not to add extra code in the original class whereas using Comparable, mandatorily we need to add the code.
Comparable interface allows us only single sorting sequence which means we can sort the collection on the basis of a single element like in an Employee table, sorting can be done on the single basis like name, employee id, date of joining, etc whereas Comparator interface provides multiple sorting sequence which means we can sort the collections on multiple bases like name, employee id, date of joining, etc.
If the user does not have access to the original code and needs to write only sorting function, Comparable can not be used for those scenarios and Comparator is the only choice for such cases.