Thread: numerical conversion methods..

ok here is a good question that i can't find an answer too. ANYWHERE. i have the following code.

import java.util.Scanner; //Imports the Scanner Device
public class MethodsProject {
 
    public static void main(String[] args) {
        Scanner keyboard = new Scanner(System.in); //names the scanner device
        int number; //declares an integer
        int decimal; //declares an integer
        int total; //declares an integer
        int input; //declares an integer
        String input2; //declares a String
        final String BINARY = "Binary"; //sets a constant string called Binary
        final String OCTAL = "Octal"; //sets a constant string called Octal
        final String HEX = "Hex"; //sets a constant string called Hex
        final String EXIT = "Exit"; //sets a constant called Exit
        String conversionType;
 
        do {
            conversionType = getConversionType(keyboard); //directs the program to the getConversionType method
 
            if (conversionType.equalsIgnoreCase(BINARY)) { //opens if binary body
                System.out.print("Enter the binary number to be converted:");
                input = keyboard.nextInt(); //gets the number from user
                decimal = getBinary(keyboard, input); //sends the input to the getBinary method
                System.out.printf("Binary number " + input + " converted to"
                        + " decimal is: " + decimal + "\n");
                keyboard.nextLine(); //clears the buffer
            } //closes the if binary body
            if (conversionType.equalsIgnoreCase(OCTAL)) { //opens the if octal body
                System.out.printf("Enter the number to be converted: ");
                input = keyboard.nextInt(); //gets the number to be converted from user
                decimal = getOctal(keyboard, input); //throws input to the getOctal method
                System.out.printf("Octal number " + input + " converted to "
                        + "decimal is: " + decimal + "\n");
                keyboard.nextLine();// clears the buffer
            } //ends the if octal body
            else if (conversionType.equalsIgnoreCase(HEX)) { //opens the if HEX body
                System.out.println("Enter the Number to be converted: ");
                input2 = keyboard.nextLine(); //gets the next string input
                // decimal = getHex(keyboard, input2);
                //System.out.printf("Hex number " + input + " converted to " +
                //        " decimal is: " + decimal + "\n");
                keyboard.nextLine(); //clears the buffer
 
            } //closes the if Hex body
        } while (!conversionType.equalsIgnoreCase(EXIT)); //ends the do-while loop
 
 
 
 
 
 
 
 
 
 
 
    } //ends main method
 
    /**
     * Get the type of conversion to be used
     * pre-condition: given valid scanner to get input from
     * post-condition: returns a conversion type of either Octal, Binary, or Hex
     * @param: a scanner representing the keyboard
     * @return: returns the conversion type
     */
    public static String getConversionType(Scanner keyboard) {//opens the body of getConversion
        String conversionType;
        final String BINARY = "Binary"; //sets a constant string called Binary
        final String OCTAL = "Octal"; //sets a constant string called Octal
        final String HEX = "Hex"; //sets a constant string called Hex
        final String EXIT = "Exit"; //sets a constant called Exit
        do { //opens a do-while loop
            System.out.printf("Enter the conversion type: (BINARY, OCTAL, HEX)"
                    + " if done type EXIT:");
            conversionType = keyboard.nextLine(); //allocates the user input to the memory slot called conversion
            if (!conversionType.equalsIgnoreCase(BINARY) //runs a check on the input for validity
                    && !conversionType.equalsIgnoreCase(OCTAL)
                    && !conversionType.equalsIgnoreCase(HEX)
                    && !conversionType.equalsIgnoreCase(EXIT)) {
                System.out.println("ERROR: Wrong Conversion Type.");
 
            } //ends the if statement
        } while (!conversionType.equalsIgnoreCase(BINARY)
                && !conversionType.equalsIgnoreCase(OCTAL)
                && !conversionType.equalsIgnoreCase(HEX)
                && !conversionType.equalsIgnoreCase(EXIT));
        return conversionType; //returns the inputed conversion type
    } //ends getConversionType method
 
    /**
     * Get the type of conversion to be used
     * pre-condition: given valid scanner input for conversion
     * post-condition: returns a value in decimal form
     * @param: a scanner representing the keyboard
     * @return: returns the decimal form of the Binary number inputed
     */
    public static int getBinary(Scanner keyboard, int input) { //opens the getBinary method
        int currentValue; //declares an integer
        int power = 0; //declares an integer
        int total = 0; //declares an integer
 
 
 
        for (int i = Integer.toString(input).length() - 1; i >= 0; i--) { //starts for loop
            currentValue = Integer.parseInt(Integer.toString(input).charAt(i) + ""); //evaluates the next int in the line
            if (currentValue > 1 || currentValue < 0) { //opens if body
                System.out.println("ERROR: The non Binary number: "
                        + input + " was entered. \n The program is ending.");
                System.exit(1); //directs the program to the runExit Method
            } //ends if statement
            total += currentValue * Math.pow(2, power); //creates a new total for each new value
            power++; //updates power to the next step
        } //ends for loop
 
        return total; //returns total
    } //ends getBinary mehtod
 
    /**
     * Get the type of conversion to be used
     * pre-condition: given valid scanner input for conversion
     * post-condition: returns a value in decimal form
     * @param: a scanner representing the keyboard
     * @return: returns the decimal form of the Octal number inputed
     */
    public static int getOctal(Scanner keyboard, int input) { //opens the body of getOctal method
        int currentValue; //declares an integer
        int power = 0;//declares an integer
        int total = 0; //declares an integer
 
 
 
        for (int i = Integer.toString(input).length() - 1; i >= 0; i--) { //starts the for loop
            currentValue = Integer.parseInt(Integer.toString(input).charAt(i) + ""); //gets a starting value
            if (currentValue > 8 || currentValue < 0) { //opens if body
                System.out.println("ERROR: The non Octal number: "
                        + input + " was entered. \n The program is ending.");
                System.exit(1); //directs the program to the runExit Method
            } //ends if statement
            total += currentValue * Math.pow(8, power); //creates a new value for total
            power++; //updates power for the next step
        } //ends for loop
 
        return total; //returns the total in decimal form
    } //ends getOctal method
 
    /**
     *Get the type of conversion to be used
     * pre-condition: given valid scanner input for conversion
     * post-condition: returns a value in decimal form
     * @param: a scanner representing the keyboard
     * @return: returns the decimal form of the Hex string inputed
     */
    public static String getHex(Scanner keyboard, String input2) { //opens the getHex method
        int currentValue;
 
        for (int i = input2.length() - 1; i >= 0; i--) { //starts the for loop
            currentValue = input2.charAt(i) + ""); //gets a starting value
            if (currentValue > 8 || currentValue < 0) { //opens if body
                System.out.println("ERROR: The non Hex digit: "
                        + input2 + " was entered. \n The program is ending.");
                System.exit(1); //directs the program to the runExit Method
            } //ends if statement
        }
        return currentValue; //returns the value
    } //ends the getHex method
} //ends class

now my teacher wants us to convert any user input from whatever form the user decides to decimal. trick is we can't use any pre-defined library codes. i.e. hexCharToDecimal, etc. we have to write the source code all by ourselves. i have binary and octal done no problem. i can't for the life of me find or figure out hex. this will be just for reference fior future becuase i have like an hour to finish this. so if anyone has any idea i would like their input