Difference Between Comparable and Comparator (With Table)

Comparable is an interface that is present in the lang package of the java language, and its purpose is to sort the collection elements using only a single attribute such as age, price, id, name, etc. It is capable of comparing it’s ownself with any other object. An object of any type, be it a list or an array, can be sorted.

Comparator is an interface that is present in the util package of the java language, and its purpose is to sort the collection elements using multiple attributes at once. It is a separate class and is external to the type of element that is being compared. The collections class provides a second sorting method that accepts a comparator as the parameter.

Comparison Table Between Comparable and Comparator

What is Comparable?

As discussed above, comparable is an interface of java programming language which is present in the lang package and is used to sort collection elements by using only one attribute. The comparable interface contains only a single method that is compareTo(). The comparable object is capable of comparing with the other objects. For the class to be able to compare the instances, it is a necessary condition for the class to implement the comparable interface.

A comparable interface was developed for the objects with natural ordering. In other words, this means that the object which is to be sorted must have the order in which it is to be sorted. In logical terms, the comparable interface compares “this” reference with the object that is mentioned in the method. When the comparable interface is implemented by any class, the object of that class can be sorted by using the Collections. sort() or the Arrays. sort() method.

The objects will automatically be sorted in the natural order that is defined by the CompareTo method. Numbers, strings, and many other types can be compared. Strings can be compared by using alphabetical comparison. Various built-in classes of java implement the comparable interface. The most important thing that should be kept in mind is that the comparable interface can only be used to compare the objects of the same class.

What is Comparator?

The comparator interface of the java programming language is present in the util package and is used to sort the collection on the basis of multiple attributes at once. Comparator is a totally separate class. The programmers use to create multiple classes that implement the comparator interface for the purpose of comparing different objects.

To compare any collection object, the first step is to create a class implementing the comparator method, which has the compare() method in it. The following step is to make an instance of that class implementing the comparator interface. The last step is to call the overloaded method, which is the sort() method and then assign both the list and the instance of the class that was created in the previous step.

The comparator interface compares two objects of different classes. The Comparator interface has two methods in it, which are the compare() method and the equals() method. The compare() method takes two different objects as its parameter to compare, and the equals() method determines whether the object being passed equals the invoking comparator. The equals() method returns a boolean value as its output. True is returned when the object passed, and the invoking object is both comparators, and if not, then false is returned.

The compare() method returns an integer value in its output which indicates the larger among the two passed objects.

Main Differences Between Comparable and Comparator

1. The comparable interface provides a single sorting sequence in which the collection can be sorted through a single element like the id, name, or any specific parameter, whereas the comparator interface provides a multiple sorting sequence in which the collection can be sorted through multiple elements like the id, name or any other parameter.
2. The comparable interface affects the original class as it modifies the actual class, whereas, on the other hand, the comparator interface does not affect the original class in any way as the actual class remains the same without any modifications.
3. A comparable interface is present in the lang package of java, whereas the comparator interface is present in the util package of java.
4. In the comparable interface compareTo() method is used to sort the elements, whereas in the comparator interface compare() method is used to sort the elements.
5. The comparable type list elements of a collection can be sorted by using the Collections. Sort (List) method, whereas on the other hand, the comparator type list elements of a collection can be sorted by using the Collections. Sort (List, Comparator) method.

Conclusion

Although both the interfaces are used for sorting purposes, they are both entirely different from one another. There are many parameters or grounds on which basis they are used differently on list elements for different purposes. If an individual wants to sort any list elements on the basis of a single element of the collection, then the comparable interface can be implemented; otherwise, if the individual wants to sort any list elements on the basis of multiple attributes, then that particular collection should be sorted implementing the comparator interface. Both the interfaces are developed to be used for separate aims to achieve.

References

1. https://dom-pubs.onlinelibrary.wiley.com/doi/abs/10.1111/j.1463-1326.2011.01545.x
2. https://journals.asm.org/doi/abs/10.1128/aac.47.6.1824-1831.2003
3. https://ieeexplore.ieee.org/abstract/document/6042862/