ArrayList order

Syntax of ArrayList sort[]

The syntax of the sort[] method is:

arraylist.sort[Comparator c]

Here, arraylist is an object of the ArrayList class.

sort[] Parameters

The sort[] method takes a single parameter.

• comparator - specifies the sort order of the arraylist

sort[] Return Values

The sort[] method does not return any value. Rather it only changes the order of elements in an arraylist.

Example 1: Sort the ArrayList in Natural Order

import java.util.ArrayList; import java.util.Comparator; class Main { public static void main[String[] args] { // create an ArrayList ArrayList languages = new ArrayList[]; // add elements to ArrayList languages.add["Python"]; languages.add["Swift"]; languages.add["C"]; languages.add["JavaScript"]; System.out.println["Unsorted ArrayList: " + languages]; // sort the ArrayList in ascending order System.out.println["Sorted ArrayList: " + languages]; } }

Output

Unsorted ArrayList: [Python, Swift, C, JavaScript] Sorted ArrayList: [C, JavaScript, Python, Swift]

In the above example, we have used the sort[] method to sort the arraylist named languages. Notice the line,

languages.sort[Comparator.naturalOrder[]];

Here, the naturalOrder[] method of the Java Comparator Interface specifies that elements are sorted in natural order [i.e. ascending order].

The Comparator interface also provides a method to sort elements in descending order. For example,

Example 2: Sort the ArrayList in Reverse Order

import java.util.ArrayList; import java.util.Comparator; class Main { public static void main[String[] args] { // create an ArrayList ArrayList languages = new ArrayList[]; // add elements to ArrayList languages.add["Python"]; languages.add["Swift"]; languages.add["C"]; languages.add["JavaScript"]; System.out.println["Unsorted ArrayList: " + languages]; // sort the ArrayList in ascending order System.out.println["Sorted ArrayList: " + languages]; } }

Output

Unsorted ArrayList: [Python, Swift, C, JavaScript] Sorted ArrayList: [Swift, Python, JavaScript, C]

Here, the reverseOrder[] method of the Comparator interface specifies that elements are sorted in reverse order [i.e. descending order].

Note: The Collections.sort[] method is the more convenient method for sorting an arraylist.