Sorting in Java

There are two in-built methods to sort in Java.

1. Arrays.Sort() works for arrays which can be of primitive data type also.
   filter_none

   edit
   close

   play_arrow

   link
   brightness_4
   code

   // A sample Java program to demonstrate working of // Arrays.sort(). // It by default sorts in ascending order. import java.util.Arrays;    public class GFG {     public static void main(String[] args)     {         int[] arr = { 13, 7, 6, 45, 21, 9, 101, 102 };            Arrays.sort(arr);            System.out.printf("Modified arr[] : %s",                           Arrays.toString(arr));     } }

   chevron_right

   filter_none

   Output:

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

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

   edit
   close

   play_arrow

   link
   brightness_4
   code

   // 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<String> al = new ArrayList<String>();         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);     } }

   chevron_right

   filter_none

Output:

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

• 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().

  Example:

  
  
  
  
  1. For Arrays.sort()
     filter_none

     edit
     close

     play_arrow

     link
     brightness_4
     code

     // 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));     } }

     chevron_right

     filter_none

     Output:

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

  2. For Collections.sort()
     filter_none

     edit
     close

     play_arrow

     link
     brightness_4
     code

     // 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<String> al = new ArrayList<String>();         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);     } }

     chevron_right

     filter_none

     Output:

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

• How to sort only a subarray?
  Example:
  filter_none

  edit
  close

  play_arrow

  link
  brightness_4
  code

  // A sample Java program to sort a subarray // using Arrays.sort(). import java.util.Arrays;    public class GFG {     public static void main(String[] args)     {         // Our arr contains 8 elements         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);            System.out.printf("Modified arr[] : %s",                           Arrays.toString(arr));     } }

  chevron_right

  filter_none

  Output:

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

• 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


How to sort objects of user defined data type?
Please refer Arrays.sort() in Java and Collections.sort() in Java for examples.

Attention reader! Don’t stop learning now. Get hold of all the important Java and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready.

RishabhPrabhu

Content Manager at LambdaTest