How to Use Comparator in Java to Sort

Sorting is a very common task in programming, and Java provides several ways to sort data, including arrays and collections.

One of the most flexible and powerful sorting methods is to use the Comparator interface, which allows you to create custom sorting rules.

In this tutorial, we will take a closer look at the Comparator interface and how to use it to sort data in Java.

What is a Comparator in Java?

The Comparator interface is a functional interface in Java that defines a single method called compare().

This method takes two objects as arguments and returns an integer value indicating the order of the two objects.

A negative value means the first object should be considered smaller than the second object, a positive value means the first object should be considered greater than the second object, and a value of zero means the two objects are equal.

How to Use Comparator in Java

To use the Comparator interface, you need to create a class that implements the Comparator interface and overrides the compare() method.

Here is an example of how to sort a list of strings in reverse alphabetical order:

import java.util.Comparator;
import java.util.Arrays;
import java.util.List;

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

public class Main {
  public static void main(String[] args) {
    List<String> words = Arrays.asList("apple", "banana", "cherry");
    words.sort(new ReverseStringComparator());
    System.out.println(words);
  }
}

This will output the following result:

[cherry, banana, apple]

In this example, the ReverseStringComparator class implements the Comparator interface and overrides the compare() method to sort the strings in reverse alphabetical order.