Arrays.sort() in Java with examples

Arrays class is a class containing static methods that are used with arrays in order to search, sort, compare, insert elements, or return a string representation of an array. So let us specify the functions first and later onwards we will be discussing the same. They are as follows being present in java.util.Arrays class. Here we will be discussing different plots using the sort() method of the Arrays class.

Arrays.sort() method consists of two variations one in which we do not pass any arguments where it sort down the complete array be it integer array or character array but if we are supposed to sort a specific part using this method of Arrays class then we overload it and pass the starting and last index to the array.

Syntax: sort() Method 

Arrays.sort(); 

Syntax: Overloaded sort() Method

public static void sort(int[] arr, int from_Index, int to_Index) ;

Parameters: It takes three parameters as can be perceived from the syntax which is as follows:

• The array to be sorted
• The index of the first element, inclusive, to be sorted (Referred to as from_index)
• The index of the last element, exclusive, to be sorted (Referred to as last_index)

Return Type: NA

Complexity Analysis:

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

Now let us see the implementation of the sort() function across different scenarios of the Arrays class as follows:

Example 1:

The original array is: 
5 -2 23 7 87 -42 509 
The sorted array is: 
-42 -2 5 7 23 87 509 

Time Complexity: O(nlog(n)) as it complexity of arrays.sort() 
Auxiliary Space : O(1)

Example 2:

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

Complexity of the above method:

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

Example 3:

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

Complexity of the above method:

Time Complexity: O(nlog(n)) as it complexity of arrays.sort()
Auxiliary Space : O(1)

Example 4:

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

Complexity of the above method:

Time Complexity: O(nlog(n)) as it complexity of arrays.sort()
Auxiliary Space : O(1)

Example 5:

Modified arr[] : 
Modified arr[] :[www.geeksforgeeks.org, practice.geeksforgeeks.org, code.geeksforgeeks.org]

Complexity of the above method:

Time Complexity: O(nlog(n)) as it complexity of arrays.sort()
Auxiliary Space : O(1)

Now lastly we will be implementing the sort() method to the fullest because here we will be declaring our own defined criteria with the help of the Comparator interface.

Example 6:

Unsorted
111 bbbb london
131 aaaa nyc
121 cccc jaipur

Sorted by rollno
111 bbbb london
121 cccc jaipur
131 aaaa nyc

Complexity of the above method:

Time Complexity: O(nlog(n)) as it complexity of arrays.sort()
Auxiliary Space : O(1)

Remember: There is a slight difference between Arrays.sort() vs Collections.sort(). Arrays.sort() works for arrays which can be of primitive data type also. Collections.sort() works for objects Collections like ArrayList, LinkedList, etc. 

Using the reverse order method: This method will sort the array in the descending. In Java Collections class also provides the reverseOrder() method to sort the array in reverse-lexicographic order.  It does not parse any parameter because static method, so we can invoke it directly by using the class name. it will sort arrays in the ascending order by the sort() method after that the reverse order() method will give us the natural ordering and we will get the sorted array in the descending order.

Syntax:

Arrays.sort(a, Collections.reverseOrder());  

Example 7:

Array in descending order: [121, 110, 99, 66, 34, 12, 12, 0, -8, -110]

Complexity of the above method:

Time Complexity: O(nlog(n)) as it complexity of arrays.sort()
Auxiliary Space : O(1)