How do I use the List.sort() method?

By Wayan in Util Package 0 Comment

The List.sort() method was introduced in Java 8. This method sorts the elements of the list on the basis of the given Comparator. If no comparator is provided, it will use the natural ordering of the elements (only if the elements are Comparable).

Let’s take a look at an example where we sort a list of integers in ascending order:

package org.kodejava.util;

import java.util.ArrayList;
import java.util.List;

public class ListSortExample {
    public static void main(String[] args) {
        List<Integer> numbers = new ArrayList<>();
        numbers.add(3);
        numbers.add(1);
        numbers.add(4);
        numbers.add(1);
        numbers.add(5);

        // Use sort() to sort the numbers in ascending order
        numbers.sort(null);

        System.out.println(numbers); 
    }
}

Outputs:

[1, 1, 3, 4, 5]

You can also pass a Comparator to List.sort(). Here’s an example where we sort a list of strings by their length:

package org.kodejava.util;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;

public class ListSortOtherExample {
    public static void main(String[] args) {
        List<String> words = new ArrayList<>();
        words.add("rat");
        words.add("elephant");
        words.add("cat");
        words.add("mouse");

        // Comparator for comparing string lengths
        Comparator<String> lengthComparator = (s1, s2) -> s1.length() - s2.length();

        // Use sort() to sort the words by their length
        words.sort(lengthComparator);

        System.out.println(words);
    }
}

Outputs:

[rat, cat, mouse, elephant]

In this case, the Comparator is a lambda expression that computes the difference in length between two strings. The List.sort() method uses this Comparator to determine the ordering of the strings in the list.

Wayan
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