Java Program to sort the given string Alphabetically using Comparator

Program

import java.util.Scanner;
import java.util.Arrays;
import java.util.Comparator;
public class SortStringsUsingComparator {
    public String sortStrings(String string)
    {
        Character tempArray[] = new Character[string.length()];
        for (int i = 0; i < string.length(); i++) {
            tempArray[i] = string.charAt(i);
        }     
        Arrays.sort(tempArray, new Comparator<Character>(){
            @Override
            public int compare(Character c1, Character c2)
            {               
                return Character.compare(c1, c2);
            }
        });
        //String str = new String(tempArray);
         // return str;
        // using StringBuilder to convert Character array to String
        StringBuilder sb = new StringBuilder(tempArray.length);
        for (Character c : tempArray)
        sb.append(c.charValue());
        return sb.toString();
    }
    public static void main(String[] args){
        SortStringsUsingComparator sortStringsUsingComparator = new SortStringsUsingComparator();
        Scanner reader = new Scanner(System.in);
        System.out.print("Enter a string to sort: ");
        String enteredString = reader.nextLine();
        String sortedString = sortStringsUsingComparator.sortStrings(enteredString);
        System.out.println("Sorted String is "+ sortedString);                
    }
}

This program sorts the characters of a given string alphabetically using a custom Comparator.

1. Input:

   • The program takes a string from the user.

2. Logic:

   • Converts the string into an array of Character objects.
   • Sorts the array using Arrays.sort() with a custom Comparator that compares characters alphabetically.
   • Converts the sorted Character array back into a string using a StringBuilder.

3. Steps:

   • Convert the input string into a Character array.
   • Use Arrays.sort() with a custom Comparator to sort characters alphabetically:
     • The comparator uses Character.compare(c1, c2) to compare two characters.
   • Convert the sorted Character array into a string using a StringBuilder.

4. Output:

   • The sorted string is printed to the user.

5. Key Features:

   • Custom Sorting:
     • The comparator allows customization if needed, such as sorting in reverse order or applying specific rules.
   • Flexible Conversion:
     • Converts from a string to a Character array and back efficiently using StringBuilder.

6. Example Execution:

   • Input:

     Enter a string to sort: banana
     

   • Process:
     • Convert "banana" to ['b', 'a', 'n', 'a', 'n', 'a'] (Character array).
     • Sort the array alphabetically using the comparator: ['a', 'a', 'a', 'b', 'n', 'n'].
     • Convert back to string: "aaabnn".
   • Output:

     Sorted String is aaabnn
     

7. Complexity:

   • Time Complexity: O(n log n) due to sorting.
   • Space Complexity: O(n) for the temporary character array and string.

8. Use Case:

   • This program can sort strings with customizable sorting rules, making it useful for tasks like case-insensitive sorting or ordering based on specific criteria.

Comparison with Arrays.sort() (Default):

• The default Arrays.sort() sorts primitive types or strings directly, whereas this program demonstrates custom sorting logic using Comparator.

Output

$ javac SortStringsUsingComparator.java
$ java SortStringsUsingComparator
Enter a string to sort: oodlescoop
Sorted String is cdeloooops