# Sorting in Java

Whenever we do hear sorting algorithms come into play such as selection sort, bubble sort, insertion sort, radix sort, bucket sort, etc but if we look closer here we are not asked to use any kind of algorithms. It is as simple sorting with the help of linear and non-linear data structures present within java. So there is sorting done with the help of brute force in java with the help of loops and there are two in-built methods to sort in Java.

Ways of sorting in Java

1. Using loops
2. Using sort() method of Arrays class
3. Using sort method of Collections class
4. Sorting on a subarray

Let us discuss all four of them and propose a code for each one of them.

Way 1: Using loops

## Java

 // Java Program to sort an elements // by bringing Arrays into play   // Main class class GFG {       // Main driver method     public static void main(String[] args)     {           // Custom input array         int arr[] = { 4, 3, 2, 1 };           // Outer loop         for (int i = 0; i < arr.length; i++) {               // Inner nested loop pointing 1 index ahead             for (int j = i + 1; j < arr.length; j++) {                   // Checking elements                 int temp = 0;                 if (arr[j] < arr[i]) {                       // Swapping                     temp = arr[i];                     arr[i] = arr[j];                     arr[j] = temp;                 }             }               // Printing sorted array elements             System.out.print(arr[i] + " ");         }     } }

Output

1 2 3 4

Time Complexity: O(N2)
Auxiliary Space: O(1)

Way 2: Using sort() method of Arrays class

Arrays.Sort() works for arrays which can be of primitive data type also which in turn by default sorts in ascending order.

Example 1

## JAVA

 // Java program to demonstrate working of // sort() method of Arrays class   // Importing Arrays class from java.util package import java.util.Arrays;   // Main class public class GFG {       // Main driver method     public static void main(String[] args)     {         // Custom input array         int[] arr = { 13, 7, 6, 45, 21, 9, 101, 102 };           // Calling the sort() method present         // inside Arrays class         Arrays.sort(arr);           // Printing and display sorted array         System.out.printf("Modified arr[] : %s",                           Arrays.toString(arr));     } }

Output

Modified arr[] : [6, 7, 9, 13, 21, 45, 101, 102]

Time Complexity: O(N log N)
Auxiliary Space: O(1)

Example 2

## JAVA

 // A sample Java program to sort an array // in descending order using Arrays.sort(). import java.util.Arrays; import java.util.Collections;   public class GFG {     public static void main(String[] args)     {         // Note that we have Integer here instead of         // int[] as Collections.reverseOrder doesn't         // work for primitive types.         Integer[] arr = { 13, 7, 6, 45, 21, 9, 2, 100 };           // Sorts arr[] in descending order         Arrays.sort(arr, Collections.reverseOrder());           System.out.printf("Modified arr[] : %s",                           Arrays.toString(arr));     } }

Output

Modified arr[] : [100, 45, 21, 13, 9, 7, 6, 2]

Time Complexity: O(N log N)
Auxiliary Space: O(1)

Way 3: Using sort() method of Collections class

Collections.sort() works for objects Collections like ArrayList and LinkedList.

Example

## JAVA

 // Java program to demonstrate working of Collections.sort() import java.util.*;   public class GFG {     public static void main(String[] args)     {         // Create a list of strings         ArrayList al = new ArrayList();         al.add("Geeks For Geeks");         al.add("Friends");         al.add("Dear");         al.add("Is");         al.add("Superb");           /* Collections.sort method is sorting the         elements of ArrayList in ascending order. */         Collections.sort(al);           // Let us print the sorted list         System.out.println("List after the use of"                            + " Collection.sort() :\n" + al);     } }

Output

List after the use of Collection.sort() :
[Dear, Friends, Geeks For Geeks, Is, Superb]

Time Complexity: O(N log N)
Auxiliary Space: O(1)

Example 2

## JAVA

 // Java program to demonstrate working of Collections.sort() // to descending order. import java.util.*;   public class GFG {     public static void main(String[] args)     {         // Create a list of strings         ArrayList al = new ArrayList();         al.add("Geeks For Geeks");         al.add("Friends");         al.add("Dear");         al.add("Is");         al.add("Superb");           /* Collections.sort method is sorting the         elements of ArrayList in ascending order. */         Collections.sort(al, Collections.reverseOrder());           // Let us print the sorted list         System.out.println("List after the use of"                            + " Collection.sort() :\n" + al);     } }

Output

List after the use of Collection.sort() :
[Superb, Is, Geeks For Geeks, Friends, Dear]

Time Complexity: O(N log N)
Auxiliary Space: O(1)

Way 4: Sorting only a subarray

## JAVA

 // Java program to sort a subarray // using Arrays.sort()   // Importing Arrays class from java.util package import java.util.Arrays;   // Main class public class GFG {       // Main drive method     public static void main(String[] args)     {         // Custom input array         int[] arr = { 13, 7, 6, 45, 21, 9, 2, 100 };           // Sort subarray from index 1 to 4, i.e.,         // only sort subarray {7, 6, 45, 21} and         // keep other elements as it is.         Arrays.sort(arr, 1, 5);           // Printing sorted array         System.out.printf("Modified arr[] : %s",                           Arrays.toString(arr));     } }

Output

Modified arr[] : [13, 6, 7, 21, 45, 9, 2, 100]

Time Complexity: O(N log N)
Auxiliary Space: O(1)

Note:

• Which sorting algorithm does Java use in sort()?
Previously, Java’s Arrays.sort method used Quicksort for arrays of primitives and Merge sort for arrays of objects. In the latest versions of Java, Arrays.sort method and Collection.sort() uses Timsort.
• Which order of sorting is done by default?
It by default sorts in ascending order.
• How to sort array or list in descending order?
It can be done with the help of Collections.reverseOrder().
• How to write my own sorting function in Java?
Please see Java programs for Quick Sort, Merge Sort, Insertion Sort, Selection Sort, Heap Sort, Bubble Sort

Feeling lost in the world of random DSA topics, wasting time without progress? It's time for a change! Join our DSA course, where we'll guide you on an exciting journey to master DSA efficiently and on schedule.
Ready to dive in? Explore our Free Demo Content and join our DSA course, trusted by over 100,000 geeks!