Java ISBN校验和生成器--无限循环？
Java ISBN校验和生成器--无限循环？
提问于 2018-10-11 08:29:51
我需要使用字符串、字符、一堆嵌套循环和条件语句为CS类构建这个ISBN校验和生成器(用于ISBN-10和ISBN-13)。在这个混乱的地方，我认为某些东西触发了无限循环，因为当我被提示输入时，我输入并按enter键，它只是转到一个新行，并期望我输入更多的数据，我猜它应该在每次成功输入后再次提示我输入另一个数据，否则告诉我它是不正确的，然后再次要求另一个输入。而且，当我输入quit时，它并不会像预期的那样结束程序并显示校验和结果，相反，它表现出与其他输入相同的行为。如果我第一次在没有给程序任何数字的情况下输入quit，它确实会正确地结束程序，但当然，输出变量的值是空的。
到目前为止，我的代码如下：
/******************************************************************************
* Program Name: Lab05A - ISBN
* Program Description: Calculate ISBN-10 AND ISBN-13
* Program Author: xxxxxxxxx
* Date Created: 10/10/2018
* Change# Change Date Programmer Name Description
* ------- ------------ ------------------- ---------------------
******************************************************************************/
package lab05a;
import java.util.Scanner;
public class Lab05A {
public static void main(String[] args) {
// Input for s
Scanner input = new Scanner(System.in); // Create new scanner
System.out.println("Enter the first 9 or 12 digits of an ISBN number. Enter QUIT to exit: "); // our ever-lasting prompt
String s = input.next(); // declare string variable "s" and set it equal to next input from user.
String output10 = null; // Declaring string output10
String output13 = null; // Declaring string output13
// main while loop
while (!"QUIT".equals(s)) { //this will run as long as the program does not receive an input of "QUIT", not case sensitive.
char checkDigit;
char checkSum = '0';
if (s.length() == 9) { //if the length of the inputted string is 9 characters...
int sum = 0; // initialize sum variable
for (int i=0; i <= s.length();) {
sum = sum + ((s.charAt(i) - '0') * (i + 1));
}
if (sum % 11 == 10) {
checkDigit = 'X';
}
else {
checkDigit = (char) ('0' + (sum % 11));
}
output10 = output10 + "\n" + s + checkDigit;
System.out.println("Enter the first 9 or 12 digits of an ISBN number. Enter QUIT to exit: ");
s = input.next();
}
else if (s.length() == 12) {
int sum = 0;
for (int i=0; i <= s.length();) {
if (i % 2 == 0) {
sum = sum + (s.charAt(i) - '0');
}
else {
sum = sum + (s.charAt(i) - '0') * 3;
}
checkSum = (char) (10 - sum % 10);
if (checkSum == 10) {
checkSum = 0;
}
output13 = "\n" + output13 + checkSum;
System.out.println("Enter the first 9 or 12 digits of an ISBN number. Enter QUIT to exit: ");
s = input.next();
}
}
else if (!s.toUpperCase().equals("QUIT")) {
System.out.println(s + " is invalid input.");
System.out.println("Enter the first 9 or 12 digits of an ISBN number. Enter QUIT to exit: ");
s = input.next();
}
}
System.out.println("The 10 digit ISBNs are \n" + output10);
System.out.println("The 13 digit ISBNs are \n" + output13);
}
}Flowchart as a separate image since it's kinda small in the instructions doc
谢谢你的帮助。
回答 1
Stack Overflow用户
发布于 2018-10-11 10:13:04
自从我在这里实现了一些建议后，更新了代码：
package lab05a;
import java.util.Scanner;
public class Lab05A {
public static void main(String[] args) {
// Input for s
Scanner input = new Scanner(System.in); // Create new scanner
System.out.println("Enter the first 9 or 12 digits of an ISBN number. Enter QUIT to exit: "); // our ever-lasting prompt
String s = input.next(); // declare string variable "s" and set it equal to next input from user.
String output10 = ""; // Declaring string output10
String output13 = ""; // Declaring string output13
// main while loop
while (!"QUIT".equalsIgnoreCase(s)) { //this will run as long as the program does not receive an input of "QUIT", not case sensitive.
char checkDigit;
char checkSum = '0';
if (s.length() == 9) { //if the length of the inputted string is 9 characters...
int sum = 0; // initialize sum variable
for (int i=0; i < s.length(); i++) {
sum = sum + ((s.charAt(i) - '0') * (i + 1));
}
if (sum % 11 == 10) {
checkDigit = 'X';
}
else {
checkDigit = (char) ('0' + (sum % 11));
}
output10 = output10 + "\n" + s + checkDigit;
System.out.println("Enter the first 9 or 12 digits of an ISBN number. Enter QUIT to exit: ");
s = input.next();
}
else if (s.length() == 12) {
int sum = 0;
for (int i=0; i < s.length(); i++) {
if (i % 2 == 0) {
sum = sum + (s.charAt(i) - '0');
}
else {
sum = sum + (s.charAt(i) - '0') * 3;
}
checkSum = (char) (10 - sum % 10);
if (checkSum == 10) {
checkSum = 0;
}
output13 = "\n" + output13 + s + checkSum;
System.out.println("Enter the first 9 or 12 digits of an ISBN number. Enter QUIT to exit: ");
s = input.next();
}
}
else if (!"QUIT".equalsIgnoreCase(s)) {
System.out.println(s + " is invalid input.");
System.out.println("Enter the first 9 or 12 digits of an ISBN number. Enter QUIT to exit: ");
s = input.next();
}
}
System.out.println("The 10 digit ISBNs are \n" + output10);
System.out.println("The 13 digit ISBNs are \n" + output13);
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/52750493
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