Tips? Criticism? All help is appreciated.

Any tips or criticisms?

class RadixConverter {
 
// command line arguments: (number) (radix of number) (radix to be converted to)
public static void main(String[] args) {
    String n = args[0];                                   // n kept as String to support alphabetic representations of numerals for larger radixes
    int startRadix = Integer.parseInt(args[1]);
    int endRadix = Integer.parseInt(args[2]);
    int decimal = convertToDecimal(n, startRadix);
    String result = convertToBase(decimal, endRadix);
    System.out.printf("%s (%d) = %s (%d)%n", n, startRadix, result, endRadix);
}

public static int convertToDecimal(String n, int startRadix) {
    int sum = 0;
    for (int i = 0; i < n.length(); i++) {                                                 // begins at first digit and ends at last digit
        char digit = n.charAt(i);
        int placeValue = (int) Math.pow(startRadix, n.length() - i - 1);                   // place value of digit's column
        if ((digit >= 48) && (digit <= 57) && (digit - 48 < startRadix)) {                 // if digit is numerical and is within specified radix
            sum += (digit - 48) * placeValue;
        } else if ((digit >= 65) && (digit <= 90) && (digit - 65 + 10 < startRadix)) {     // if digit is alphabetic and within specified radix
            sum += (digit - 55) * placeValue;
        } else {
            throw new IllegalArgumentException("\n\nThe input number is invalid or contains digits outside of its specified radix.\n");
        }
    }
    return sum;
}

public static String convertToBase(int decimal, int endRadix) {
    StringBuilder sb = new StringBuilder("");
    do {
        int rem = decimal % endRadix;
        if ((rem <= 9) && (endRadix <= 36) && (endRadix >= 2)) {
            sb.append(Integer.toString(rem));
        } else if ((rem <= 35) && (endRadix <= 36) && (endRadix >= 2)) {
            sb.append((char) (rem + 55));
        } else {
            throw new IllegalArgumentException("\n\nThe output radix must be from 2 to 36.\n");
        }
        decimal /= endRadix;
    } while (decimal != 0);
    return reverseOrder(sb.toString());
}

public static String reverseOrder(String s) {
    StringBuilder sb = new StringBuilder("");
    for (int i = s.length() - 1; i >= 0; i--) {    // executes each character in reverse order
        sb.append(s.charAt(i));
    }
    return sb.toString();
}

}

class RadixConverter {
    // command line arguments: (number) (radix of number) (radix to be converted to)
    public static void main(String[] args) {
        String n = args[0];                                   // n kept as String to support alphabetic representations of numerals for larger radixes
        int startRadix = Integer.parseInt(args[1]);
        int endRadix = Integer.parseInt(args[2]);
        int decimal = convertToDecimal(n, startRadix);
        String result = convertToBase(decimal, endRadix);
        System.out.printf("%s (%d) = %s (%d)%n", n, startRadix, result, endRadix);
    }

    public static int convertToDecimal(String n, int startRadix) {
        int sum = 0;
        for (int i = 0; i < n.length(); i++) {                                                 // begins at first digit and ends at last digit
            char digit = n.charAt(i);
            int placeValue = (int) Math.pow(startRadix, n.length() - i - 1);                   // place value of digit's column
            if ((digit >= 48) && (digit <= 57) && (digit - 48 < startRadix)) {                 // if digit is numerical and is within specified radix
                sum += (digit - 48) * placeValue;
            } else if ((digit >= 65) && (digit <= 90) && (digit - 65 + 10 < startRadix)) {     // if digit is alphabetic and within specified radix
                sum += (digit - 55) * placeValue;
            } else {
                throw new IllegalArgumentException("\n\nThe input number is invalid or contains digits outside of its specified radix.\n");
            }
        }
        return sum;
    }

    public static String convertToBase(int decimal, int endRadix) {
        StringBuilder sb = new StringBuilder("");
        do {
            int rem = decimal % endRadix;
            if ((rem <= 9) && (endRadix <= 36) && (endRadix >= 2)) {
                sb.append(Integer.toString(rem));
            } else if ((rem <= 35) && (endRadix <= 36) && (endRadix >= 2)) {
                sb.append((char) (rem + 55));
            } else {
                throw new IllegalArgumentException("\n\nThe output radix must be from 2 to 36.\n");
            }
            decimal /= endRadix;
        } while (decimal != 0);
        return reverseOrder(sb.toString());
    }

    public static String reverseOrder(String s) {
        StringBuilder sb = new StringBuilder("");
        for (int i = s.length() - 1; i >= 0; i--) {    // executes each character in reverse order
            sb.append(s.charAt(i));
        }
        return sb.toString();
    }
}