How do I sort items of an ArrayList?

This example shows you how we can sort items of an ArrayList using the Collections.sort() method. Beside accepting the list object to be sorted we can also pass a Comparator implementation to define the sorting behaviour such as sorting in descending or ascending order.

package org.kodejava.util;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class ArrayListSortExample {
    public static void main(String[] args) {
        /*
         * Create a collections of colours
         */
        List<String> colours = new ArrayList<>();
        colours.add("red");
        colours.add("green");
        colours.add("blue");
        colours.add("yellow");
        colours.add("cyan");
        colours.add("white");
        colours.add("black");

        /*
         * We can sort items of a list using the Collections.sort() method.
         * We can also reverse the order of the sorting by passing the
         * Collections.reverseOrder() comparator.
         */
        Collections.sort(colours);
        System.out.println(Arrays.toString(colours.toArray()));

        colours.sort(Collections.reverseOrder());
        System.out.println(Arrays.toString(colours.toArray()));
    }
}

The code will output:

[black, blue, cyan, green, red, white, yellow]
[yellow, white, red, green, cyan, blue, black]