我的收银程序出了问题，我想要求用户输入一些数量，只限于4。
我目前的问题是：
我应该如何修复我的程序，以便即使我的命令仍在循环，用户也只能输入最多4个。
无论如何，这是我的代码。
public static void main(String[] args) {
Scanner scan = new Scanner(new InputStreamReader(System.in,Charset.defaultCharset()));;
Scanner choiz = new Scanner(System.in);
Scanner pay = new Scanner(System.in);
double total = 0;
double totalA = 0;
double totalB = 0;
double totalC = 0;
double totalD = 0;
double totalE = 0;
double A = 3.25;
double B = 5.00;
double C = 3.00;
double D = 1.50;
double E = 4.50;
char choice;
char choice2;
double payment = 0;
double change = 0;
int numb;
do {
System.out.println("|------------------------------------|");
System.out.println("| MENU |");
System.out.println("|------------------------------------|");
System.out.println("| Press | Product |");
System.out.println("|------------------------------------|");
System.out.println("| A | Product A 3.25 |");
System.out.println("| B | Product B 5.00 |");
System.out.println("| C | Product C 3.00 |");
System.out.println("| D | Product D 1.50 |");
System.out.println("| E | Product E 4.50 |");
System.out.println("|------------------------------------|");
System.out.println("| R | Receipt |");
System.out.println("|------------------------------------|");
System.out.println();
System.out.println("Enter Choice:");
choice = choiz.next().toUpperCase().charAt(0);
switch (choice) {
case 'A':
System.out.println("Item A Selected!");
System.out.println("Please enter number of item/s: ");
//numb = scan.nextInt();
while (!scan.hasNextInt()) {
scan.next();
System.out.print("Please enter an integer: ");
}
numb = scan.nextInt();
if (numb <= 4) {
totalA = numb * A;
System.out.println("Current Total: " + totalA);
}
else {
System.out.println("Only accepting 4 items and below!");
}
break;
case 'B':
System.out.println("Item B Selected!");
System.out.println("Please enter number of item/s: ");
numb = scan.nextInt();
if (numb <= 4) {
totalB = numb*B;
System.out.println("Current Total: " + totalB);
}
else {
System.out.println("Only accepting 4 items and below!");
}
break;
case 'C':
System.out.println("Item C Selected!");
System.out.println("Please enter number of item/s: ");
numb = scan.nextInt();
if (numb <= 4) {
totalC = numb * C;
System.out.println("Current Total: " + totalC);
}
else {
System.out.println("Only accepting 4 items and below!");
}
break;
case 'D':
System.out.println("Item D Selected!");
System.out.println("Please enter number of item/s: ");
numb = scan.nextInt();
if (numb <= 4) {
totalD = numb * D;
System.out.println("Current Total: " + totalD);
}
else {
System.out.println("Only accepting 4 items and below!");
}
break;
case 'E':
System.out.println("Item E Selected!");
System.out.println("Please enter number of item/s: ");
numb = scan.nextInt();
if (numb <= 4) {
totalE = numb * E;
System.out.println("Current Total: " + totalE);
}
else {
System.out.println("Only accepting 4 items and below!");
}
break;
case 'R':
System.out.println("=====================================");
System.out.println("| Receipt for purchase |");
System.out.println("=====================================");
break;
default:
System.out.println("Invalid selection!");
}
}
while (choice != 'R');
total = totalA + totalB + totalC + totalD + totalE;
System.out.println("You purchased the following:");
System.out.println("Item A \t" + "Amount: " + totalA);
System.out.println("Item B \t" + "Amount: " + totalB);
System.out.println("Item C \t" + "Amount: " + totalC);
System.out.println("Item D \t" + "Amount: " + totalD);
System.out.println("Item E \t" + "Amount: " + totalE);
System.out.println("\t\t=====================================");
System.out.println("\t\t| Total bill to pay: " + total + "|");
System.out.println("\t\t=====================================");
System.out.println("Enter your Payment: ");
payment = pay.nextInt();
if(payment > total || payment == total){
change = payment - total;
System.out.println(" Your Payment is " + payment + " and your change is " + change);
System.out.println("[---Thank You for Ordering---]");
}
else{
do{
System.out.println("Insufficient amount of Payment!");
System.out.println("Press [Y] to Try again or [N] to Exit: ");
choice2 = choiz.next().toUpperCase().charAt(0);
switch(choice2)
{
case 'Y': System.out.println("--continue--");
break;
case 'N': System.out.println("--bye--");
Runtime.getRuntime().halt(0);
break;
default:System.out.println("Invalid selection!");
}
}while(choice2!='Y');
System.out.println("Enter your Payment: ");
payment = pay.nextInt();
change = payment - total;
System.out.println(" Your Payment is " + payment + " and your change is " + change);
System.out.println("[---Thank You for Ordering---]");
}}
答案 0 :(得分：1)
你可以这样做，
首先初始化4个变量以跟踪订单，
case然后在每个quantity语句中，在获得用户对A的输入后，从适当的变量中减去他订购的金额。
例如在A_left -= numb; // subtract the amount(quantity ordered)
if (A_left < 0) {
System.out.println("You can only choose 4 items max from A");
break;
}
的情况下，
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
希望这有帮助！