Java Program For Case Specific Sorting

// Java Program for Case Specific Sorting
// using Collections.sort(list) method

// Importing input output classes
// Importing utility classes
import java.io.*;
import java.util.*;

class GFG {

    // Method 1
    // To sort the string
    static String sortString(String str)
    {
        // Creating two Arraylist  class objects
        // Declaring object of character type
        ArrayList<Character> list = new ArrayList<>();
        ArrayList<Character> list2 = new ArrayList<>();

        // Initially the string is empty
        String res = "";

        // Iterating over the string
        for (int i = 0; i < str.length(); i++) {
            // Finding character at indexes
            // using charAt() method in List object
            if (str.charAt(i) >= 'a'
                && str.charAt(i) <= 'z')
                list.add(str.charAt(i));

            if (str.charAt(i) >= 'A'
                && str.charAt(i) <= 'Z')
                list2.add(str.charAt(i));
        }

        // Sorting the Collection interface
        // using sort() method
        Collections.sort(list);
        Collections.sort(list2);

        int i = 0;
        int j = 0;

        // iterating over string using length() method
        for (int k = 0; k < str.length(); k++) {

            // If lowercase character encountered
            if (str.charAt(k) >= 'a'
                && str.charAt(k) <= 'z') {

                // Appending them all in beginning of string
                res += list.get(i);
                ++i;
            }

            // If uppercase character encountered
            else if (str.charAt(k) >= 'A'
                     && str.charAt(k) <= 'Z') {

                // Appending them all together after
                // lowercase is finished in input string
                res += list2.get(j);
                ++j;
            }
        }
        return res;
    }

    // Method 2
    // Main driver method
    public static void main(String[] args)
    {

        // Passing the custom string as input for which we
        // want case-specific sorting by calling the method
        // 1 as defined above
        System.out.println(sortString("defRTSersUXI"));
    }
}