Decoder

package FinalExamPrep;

import java.util.Scanner;

public class Charity {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        String encrypted = scanner.nextLine();
        String command = scanner.nextLine();

        while (!command.equals("Finish")) {
            String[] commandParts = command.split(" ");
            String commandName = commandParts[0];

            switch (commandName) {
                case "Replace":
                    encrypted = replace(encrypted, commandParts[1].charAt(0), commandParts[2].charAt(0));
                    break;
                case "Cut":
                    int startIndex = Integer.parseInt(commandParts[1]);
                    int endIndex = Integer.parseInt(commandParts[2]);
                    encrypted = cut(encrypted, startIndex, endIndex);
                    break;
                case "Make":
                    encrypted = make(encrypted, commandParts[1]);
                    break;
                case "Check":
                    check(encrypted, commandParts[1]);
                    break;
                case "Sum":
                    int startSumIndex = Integer.parseInt(commandParts[1]);
                    int endSumIndex = Integer.parseInt(commandParts[2]);
                    sum(encrypted, startSumIndex, endSumIndex);
                    break;
            }
            command = scanner.nextLine();
        }
    }

    private static void sum(String current, int startIndex, int endIndex) {
        int len = current.length();
        if (!isValidIndex(startIndex, len)) {
            System.out.println("Invalid indexes!");
            return;
        } else if (!isValidIndex(endIndex, len)) {
            System.out.println("Invalid indexes!");
            return;
        }

        int sum = 0;


        for (int i = startIndex; i <= endIndex; i++ ){
            sum += current.charAt(i);

        }

        System.out.println(sum);
    }

    private static void check(String current, String search) {
       int searchIndex = current.indexOf(search);

       if (searchIndex == - 1){
           System.out.println("Message doesn't contain " + search);
       }else{
           System.out.println("Message contains " + search);
       }
    }

    private static String make(String current, String targetCase) {
        String result;
        if (targetCase.equals("Upper")) {
            result = current.toUpperCase();
        } else {
            result = current.toLowerCase();
        }

        System.out.println(result);

        return result;
    }

    private static String cut(String current, int startIndex, int endIndex) {
        int len = current.length();
        if (!isValidIndex(startIndex, len)) {
            System.out.println("Invalid indexes!");
            return current;
        } else if (!isValidIndex(endIndex, len)) {
            System.out.println("Invalid indexes!");
            return current;
        }

        String firstPart = current.substring(0, startIndex);
        String secondPart = current.substring(endIndex + 1, len);

        String result = firstPart + secondPart;

        System.out.println(result);

        return result;

    }

    private static boolean isValidIndex(int toCheck, int length) {
        return toCheck >= 0 && toCheck < length;
    }

    private static String replace(String current, char searchFor, char replaceWith) {
        String result = current.replace(searchFor, replaceWith);

        System.out.println(result);

        return result;
    }
}