Difference Between Comparable and Comparator in Java

In Java programming, two interfaces are used to specify the behaviour in which classes will be implemented: comparator and comparable. The Comparator interface enables sorting by taking an object’s properties into account, whereas Comparable is used on naturally ordered objects. Additionally, Comparable compares items using the “this” reference, while Comparator sorting considers objects of two different types. 

Now that we know the basic principle behind both interfaces, let’s see how they differ from one another. Check out our Java course online training to learn more.

When to Use Comparable in Java?

Knowing when to use Comparable is crucial when contrasting comparator versus comparable in Java. You have to select the Comparable interface if you wish to sort the components in the default natural sorting order. The rationale is that in order to use the default natural sorting order, the object needs to be both similar and homogenous. It is important to remember that if an object’s class makes use of the Comparable interface, then it is deemed comparable. Every String and Wrapper class by default implements the Comparable interface. Therefore, you do not need to implement a Comparable interface if you need to sort the String element.

When to use a Comparator in Java?

You must first understand the differences between comparable and comparator in Java in order to avoid confusion regarding the interface being used. To assist in sorting the objects of the user-defined classes, there is a comparator interface. Two items belonging to the same class can be compared by the associated comparator object. 

As an illustration, let’s say you have an Array/ArrayList of a class with fields like name, address, DOB, roll number, etc. Sorting the array by name or Roll number is what you want to do now. You now have to decide between Java’s comparator and comparable methods. You can arrange the objects in a user-defined class in a certain order with the usage of a comparator interface.

When to use a Comparable and Comparator interface in Java programming?

You need to know which interface to choose and how to use a comparator and comparable ones. It is advisable to use a comparable interface if you have a fixed requirement, such as the need for the class objects to be sorted based on a single field, and you expect this requirement to remain constant going forward.  It is advised to utilise the multiple comparator class directly if sorting class objects through several fields is necessary.

Because a comparator class offers versatility, you can use it to override objects and build numerous comparator classes. Conversely, a comparable interface is fixed. While contrasting comparator and comparable in Java, this is a crucial distinction to make.

Difference Between Comparable and Comparator

1.Method of Sorting

Comparable

It sorts using the compareTo() function. Within the Comparable sorting interface, this is the only available way. 

compareTo(Object O) compares one object to another of the same type when it receives an object as an argument. You can only compare an object of the same type with another object if it is a string. With an int object, similarly, and so forth. Depending on the outcome of the sorting, compareTo() produces an integer value that is zero, positive, or negative. 

This function yields an int value that can be either -1, 0 or 1.

• If the value of this object is less than the value of the given object, the output is -1.
• If the value of this object and the given object are the same, the output is 0.
• If the value of this object is higher than the value of the given object, the output is 1.

Comparator

Comparator has two methods for sorting elements: equals() and compare(). 

You need to be aware of when to utilise each comparison tool when comparing comparator and comparative. When you require a different sorting order for bespoke objects than the default ordering based on several fields, you often use a comparator interface.

Compare(Object O1, Object O2) considers two input parameters and yields the intended result. To show how the first and second arguments compare, it returns an integer. 

• An integer that is negative is returned if O1 is smaller than O2.
• An integer that is positive will be returned if O1 is bigger than O2.
• It yields 0 if O1 and O2 are equal.

equals(Object) compares an object to the comparator using the object as input. If the Object and the Comparator are equal, it returns True. It also guarantees that the sequence remains unchanged. 

This is the syntax:

equals (boolean) on object obj

Here, the object you wish to test for equality is denoted by obj. If both obj and the called object are Comparator objects and use the same ordering, then this function returns true. It returns false otherwise.

Note: Most simple comparators don’t use overriding equals() because it is pointless.

2.Package Used

Comparable

It is present in the java.lang package of Java. 

Comparator

It is present in the java.util package of Java.

3.Ordering and Class

Comparable

• It considers items that exhibit natural ordering, or a propensity to arrange themselves. For instance, names, prices, salaries, roll numbers, ages, and so on might be arranged in alphabetical or numeric order. 
• The fact that both objects are members of the same class is also crucial.
• A comparable interface contrasts the reference “this” with the given item. 
• Comparable sorting has an impact on the class as a whole. 

Comparator

• The main purpose of this interface is to sort the characteristics of certain objects. They can be customised; a natural order is not necessary. 
• You must override the compare method for the Comparator interface (obj).
• To compare the attributes of the objects in the two classes under consideration, the sorting logic must be in distinct classes.
• The actual class is not affected.

4.Sequences and Collections

Comparable

• Only single sorting sequences are supported. This suggests that you can only take into account a single collection element or attribute, like a roll number, age, or rank.
• You can use Collection. sort(List) or Arrays. sort(List) to sort a collection of objects, arrays, or lists. The items will revert to their original order as a result.

Comparator

• Multiple sorting sequences are supported. This suggests that you can take into account several components or characteristics of a collection, including rank, age, and roll number.
• A collection is useful to you.To sort a collection, use sort(list, comparator).

Other points of difference between Comparator and Comparable

• One of the main ways that comparable differs from comparator is that you can only use one comparison while using comparable. However, you can construct multiple custom comparators for a particular type according to your needs. If so, each custom comparator will employ a different sorting interpretation. For instance, you can utilise many attributes in the comparator but only one attribute in the comparative example.
• Comparator and similar interfaces differ in that the former can be used to provide a single sorting option, while the latter can provide several sorting options.When use Comparable, class is necessary for implementation. However, while using the Comparator, you need not make any modifications in the class.
• Another difference between comparable and comparator is found in the way the interface is put into practice. Every wrapper class and String class implements a similar interface. Additionally, bespoke items sort using a similar interface. Conversely, the custom objects are mostly sorted using the comparator interface. It can also be used to compare items from various classes. 
• Additionally, sorting objects in many fields is a good application of the comparator interface, which highlights the main distinctions between comparator and comparable in Java.

Things To Keep In Mind While Using Comparable And Comparator In Java

• If you are selling to carry out a standard comparison for a particular class, the comparable interface is the better choice.
• Comparator permits lambda usage. 
• Both Comparator and Comparable can be implemented using the compareTo() method.
• It is advised to use a comparator interface if you want sorting flexibility.

Conclusion When we sort in most real-world situations, we often have a number of criteria in mind. Comparator, which lets you select and modify several sorting techniques to meet your needs, is more practical than default sorting, which uses comparable results and cannot be dynamically modified. Comparator outperforms Comparable in terms of useful applications simply because of this. To learn more, check out our Java course online.