CSC-111 HW6 ISBN Number Generator

ISBNGenerator.java

/*
 * A.C. Silvestri
 * CSC 111
 * 11/04/2018
 * Generate Proper ISBN Numbers
 * silvestri@stcc.edu
 * Check using:  http://www.hahnlibrary.net/libraries/isbncalc.html
 */

import java.util.Scanner;

public class ISBNGenerator {
	
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		String isbn;
		
		boolean isValid;
		do {
			System.out.print("Enter 12 digits: ");
			isbn = input.nextLine().trim();
			if (isbn.length() == 12) {
				isValid = true;
				for (int i = 0; isValid && i < 12; i++)
					if (!Character.isDigit(isbn.charAt(i)))
							isValid = false;
			}
			else 
				isValid = false;
			if (!isValid) 
				System.out.println("Sorry, bad input.");
		} while (!isValid);
		
		// If execution comes here, it's guaranteed to be a
		// 12 digit string
		
		int sum = 0;
		for (int i = 0; i < isbn.length(); i++) {
			int digitValue = isbn.charAt(i) - '0';
			if (i % 2 == 0)
				sum += digitValue;
			else
				sum += 3 * digitValue;
		}
		int checkSum = 10 - sum % 10;
		isbn += checkSum == 10 ? '0' : (char)(checkSum + '0');
	
		System.out.printf("ISBN = %s\n", isbn);		
		input.close();
	}
}

ISBNGenerator2.java

/*
 * A.C. Silvestri
 * CSC 111
 * 11/04/2018
 * Generate Proper ISBN Numbers
 * silvestri@stcc.edu
 * Check using:  http://www.hahnlibrary.net/libraries/isbncalc.html
 */

import java.util.Scanner;

public class ISBNGenerator2 {
	
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		String isbn;
		
		do {
			System.out.print("Enter 12 digits: ");
			isbn = input.nextLine().trim();
			if (isbn.length() == 12) {
				boolean isValid = true;
				for (int i = 0; isValid && i < 12; i++)
					if (!Character.isDigit(isbn.charAt(i)))
							isValid = false;
				if (isValid)
					break;
			}
			System.out.println("Sorry, bad input.");
		} while (true);
		
		// If execution comes here, it's guaranteed to be a
		// 12 digit string
		
		int sum = 0;
		for (int i = 0; i < isbn.length(); i++) {
			int digitValue = isbn.charAt(i) - '0';
			if (i % 2 == 0)
				sum += digitValue;
			else
				sum += 3 * digitValue;
		}
		int checkSum = 10 - sum % 10;
		isbn += checkSum == 10 ? '0' : (char)(checkSum + '0');
	
		System.out.printf("ISBN = %s\n", isbn);		
		input.close();
	}
}

ISBNGenerator3.java

/*
 * A.C. Silvestri
 * CSC 111
 * 11/04/2018
 * Generate Proper ISBN Numbers
 * silvestri@stcc.edu
 * Check using:  http://www.hahnlibrary.net/libraries/isbncalc.html
 */

import java.util.Scanner;

public class ISBNGenerator3 {

	private static boolean isISBNStringValid(String isbn) {
		boolean isValid;
		if (isbn.length() == 12) {
			isValid = true;
			for (int i = 0; isValid && i < 12; i++)
				if (!Character.isDigit(isbn.charAt(i)))
					isValid = false;
		}
		else
			isValid = false;
		return isValid;
	}
	
	private static int calcCheckSum(String isbn) {
		int sum = 0;
		for (int i = 0; i < isbn.length(); i++) {
			int digitValue = isbn.charAt(i) - '0';
			if (i % 2 == 0)
				sum += digitValue;
			else
				sum += 3 * digitValue;
		}
		int checkSum = 10 - sum % 10;
		return checkSum;
	}
	
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		String isbn;

		boolean isValid;
		do {
			System.out.print("Enter 12 digits: ");
			isbn = input.nextLine().trim();
			isValid = isISBNStringValid(isbn);
			if (!isValid)
				System.out.println("Sorry, bad input.");
		} while (!isValid);

		// If execution comes here, it's guaranteed to be a
		// 12 digit string
		
		int checkSum = calcCheckSum(isbn);
		isbn += checkSum == 10 ? '0' : (char) (checkSum + '0');

		System.out.printf("ISBN = %s\n", isbn);
		input.close();
	}


}