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Table of contents
1.
Introduction
2.
The Basics of Comparator
2.1.
Creating a User-Defined Class
2.2.
Crafting a Generic Comparator
2.3.
Sorting with Comparator
3.
Frequently Asked Questions
3.1.
What is a Comparator in Java?
3.2.
What does a Generic Comparator do?
3.3.
How is the compare method used in the Comparator interface?
4.
Conclusion
Last Updated: Mar 27, 2024
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Generic Comparator in Java

Author Gunjan Batra
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Introduction

When working with Java, Sorting is an essential operation that every developer needs to understand. Thankfully, Java provides robust tools and interfaces to make this task easier. One such tool is the Comparator interface. 

Generic Comparator in java

This article will explore how we can create a generic Comparator to compare objects of a user-defined class in Java.

The Basics of Comparator

The Comparator interface in Java is used for sorting collections of objects. It allows you to order objects based on user-defined conditions, adding a level of customization to the sorting process. A typical Comparator interface might look like this:

Comparator<T> {
    int compare(T o1, T o2);
}

The compare method takes two objects for comparison and returns an integer. If the return value is negative, o1 is less than o2. If it's zero, both are equal. If it's positive, o1 is greater than o2.

Creating a User-Defined Class

Let's create a user-defined class Student which we'll later sort using our generic comparator.

public class Student {
    private String name;
    private int age;


    // constructor, getters and setters
}

Crafting a Generic Comparator

A generic comparator is a flexible tool that allows sorting by different attributes of a user-defined class. Let's create a generic comparator StudentComparator for our Student class.

public class StudentComparator implements Comparator<Student> {
    @Override
    public int compare(Student s1, Student s2) {
        return s1.getName().compareTo(s2.getName());
    }
}

Here, the StudentComparator compares Student objects based on their names. You can change this comparison criterion according to your requirements.

Sorting with Comparator

Now that we have a comparator, we can use it to sort a list of students:

List<Student> students = // initialization
Collections.sort(students, new StudentComparator());

The above line will sort the students list based on the students' names in alphabetical order.

Also see,  Eclipse ide for Java Developers

Also Read, addition of two numbers in java

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Frequently Asked Questions

What is a Comparator in Java?

A Comparator in Java is an interface used to sort collections of objects based on user-defined conditions.

What does a Generic Comparator do?

A Generic Comparator allows you to compare objects of a user-defined class based on different attributes.

How is the compare method used in the Comparator interface?

The compare method takes two objects and returns an integer indicating whether the first object is less than, equal to, or greater than the second object.

Conclusion

In Java, the Comparator interface provides a powerful way to sort collections of objects. A generic comparator adds flexibility, enabling sorting by different attributes of a user-defined class. By implementing the compare method, you dictate the sorting logic, which could be anything from alphabetical order to numerical order. This flexibility makes the Comparator interface a vital tool in every Java programmer's toolkit. Whether you're a beginner or a seasoned developer, understanding how to use and create generic comparators can enhance your programming skills and allow you to write more adaptable code.

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