问题描述
- B - 检查余额
- D - 存款
- W - 提款
- Q - 退出
它们的功能基本上就是它们的名字。有两种方法可以终止程序:通过输入“Q”和“N”。但是我对 Q - Quit 选项有疑问。这是源代码:
Scanner scan = new Scanner (system.in);
char anotherTransact = 0,option;
int balance = 100000,deposit = 0,withdraw = 0;
do {
System.out.println("\nWelcome to ABC BANK \n");
System.out.println("B - Check for Balance");
System.out.println("D - Make Deposit");
System.out.println("W - Make Withdraw");
System.out.println("Q - Quit");
System.out.print("\nSelect an option : ");
option = scan.next().charat(0);
if ((option == 'B') || (option == 'b')) {
System.out.println("\nYour current balance is " +balance);
}
else if ((option == 'D') || (option == 'd')) {
System.out.print("\nEnter amount to Deposit : ");
deposit = scan.nextInt();
if (deposit > 1 && deposit <= 500000) {
System.out.println("Deposit Transaction is successfully completed.");
balance = balance + deposit;
}
else if (deposit > 500000) {
System.out.println("Deposit Amount must not be greater than 500,000");
}
else {
System.out.println("Deposit must be greater than zero");
}
}
else if ((option == 'W') || (option == 'w')) {
System.out.print("\nEnter amount to Withdraw : ");
withdraw = scan.nextInt();
if ((withdraw % 100 == 0 && withdraw < 150000)) {
System.out.println("Withdrawal Transaction is successfully completed.");
balance = balance - withdraw;
}
else if (withdraw > 150000) {
System.out.println("Withdrawal Amount must not be greater then 150,000");
}
else if (withdraw < 0) {
System.out.println("Withdrawal Amount must be greater than zero");
}
else {
System.out.println("Withdawal Amount must be divisible by 100");
}
}
else if ((option == 'Q') || (option == 'q'))
break;
else {
System.out.println("\nInvalid entry,enter any valid option : (B/D/W/Q)");
}
System.out.print("\nWant to Transact another (Y/N?) ");
anotherTransact = scan.next().charat(0);
System.out.println("\n======================================================");
}
while ((anotherTransact == 'Y') || (anotherTransact =='y'));
if ((anotherTransact == 'N' || anotherTransact == 'n')) {
System.out.println("\nThank you for using this program!");
}
else {
System.out.println("Invalid entry,entery any valid option : (Y/N)");
}
scan.close();
它的输出是这样的:
Welcome to ABC BANK
B - Check for Balance
D - Make Deposit
W - Make Withdraw
Q - Quit
Select an option :
当我输入Q选项时,输出应该是这样的:
Welcome to ABC BANK
B - Check for Balance
D - Make Deposit
W - Make Withdraw
Q - Quit
Select an option : Q
======================================================
Thank you for using this program!
但是当我输入它时,它会说这是一个无效的输入。我应该怎么做才能通过输入“Q”来结束程序?
解决方法
你的 Q 实现是正确的,它会退出 do while 循环,但是在 while 语句之后你有一个 if:
if ((anotherTransact == 'N' || anotherTransact == 'n')) {
System.out.println("\nThank you for using this program!");
}
else {
System.out.println("Invalid entry,entery any valid option : (Y/N)");
}
当您键入 Q 退出循环时,anotherTransact
不等于 'N',因此它将进入 else 并打印无效条目。如果我理解正确的话,在 while 语句之后您实际上并不需要:
System.out.println("\n======================================================");
System.out.println("\nThank you for using this program!");
,
您的代码有两个问题:
-
将以下代码置于
do-while
循环范围之外:if ((anotherTransact == 'N' || anotherTransact == 'n')) { System.out.println("\nThank you for using this program!"); } else { System.out.println("Invalid entry,entery any valid option : (Y/N)"); }
然而,仅仅纠正这个问题是不够的。检查下一点/问题以了解需要做什么才能使其按您的预期工作。
-
在无效输入的情况下不循环:您需要另一个循环(我建议如下所示的
do-while
循环)来纠正这个问题。boolean valid; do { valid = true; System.out.print("\nWant to Transact another (Y/N?) "); anotherTransact = scan.next().charAt(0); System.out.println("\n======================================================"); if (anotherTransact == 'N' || anotherTransact == 'n') { System.out.println("\nThank you for using this program!"); } else if (!(anotherTransact == 'Y' || anotherTransact == 'y')) { System.out.println("Invalid entry,entery any valid option : (Y/N)"); valid = false; } } while (!valid);
完整的更新代码:
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
char anotherTransact = 0,option;
int balance = 100000,deposit = 0,withdraw = 0;
do {
System.out.println("\nWelcome to ABC BANK \n");
System.out.println("B - Check for Balance");
System.out.println("D - Make Deposit");
System.out.println("W - Make Withdraw");
System.out.println("Q - Quit");
System.out.print("\nSelect an option : ");
option = scan.next().charAt(0);
if ((option == 'B') || (option == 'b')) {
System.out.println("\nYour current balance is " + balance);
} else if ((option == 'D') || (option == 'd')) {
System.out.print("\nEnter amount to Deposit : ");
deposit = scan.nextInt();
if (deposit > 1 && deposit <= 500000) {
System.out.println("Deposit Transaction is successfully completed.");
balance = balance + deposit;
} else if (deposit > 500000) {
System.out.println("Deposit Amount must not be greater than 500,000");
} else {
System.out.println("Deposit must be greater than zero");
}
} else if ((option == 'W') || (option == 'w')) {
System.out.print("\nEnter amount to Withdraw : ");
withdraw = scan.nextInt();
if ((withdraw % 100 == 0 && withdraw < 150000)) {
System.out.println("Withdrawal Transaction is successfully completed.");
balance = balance - withdraw;
} else if (withdraw > 150000) {
System.out.println("Withdrawal Amount must not be greater then 150,000");
} else if (withdraw < 0) {
System.out.println("Withdrawal Amount must be greater than zero");
} else {
System.out.println("Withdawal Amount must be divisible by 100");
}
} else if ((option == 'Q') || (option == 'q')) {
break;
} else {
System.out.println("\nInvalid entry,enter any valid option : (B/D/W/Q)");
}
boolean valid;
do {
valid = true;
System.out.print("\nWant to Transact another (Y/N?) ");
anotherTransact = scan.next().charAt(0);
System.out.println("\n======================================================");
if (anotherTransact == 'N' || anotherTransact == 'n') {
System.out.println("\nThank you for using this program!");
} else if (!(anotherTransact == 'Y' || anotherTransact == 'y')) {
System.out.println("Invalid entry,entery any valid option : (Y/N)");
valid = false;
}
} while (!valid);
} while (anotherTransact == 'Y' || anotherTransact == 'y');
}
}
示例运行:
Welcome to ABC BANK
B - Check for Balance
D - Make Deposit
W - Make Withdraw
Q - Quit
Select an option : b
Your current balance is 100000
Want to Transact another (Y/N?) d
======================================================
Invalid entry,entery any valid option : (Y/N)
Want to Transact another (Y/N?) d
======================================================
Invalid entry,entery any valid option : (Y/N)
Want to Transact another (Y/N?) y
======================================================
Welcome to ABC BANK
B - Check for Balance
D - Make Deposit
W - Make Withdraw
Q - Quit
Select an option : d
Enter amount to Deposit : 200
Deposit Transaction is successfully completed.
Want to Transact another (Y/N?) y
======================================================
Welcome to ABC BANK
B - Check for Balance
D - Make Deposit
W - Make Withdraw
Q - Quit
Select an option : b
Your current balance is 100200
Want to Transact another (Y/N?) n
======================================================
Thank you for using this program!
一些附加说明:
-
您应该永远不要关闭
Scanner
的System.in
,因为它也会关闭System.in
并且无法在不重新启动的情况下再次打开它JVM。但是,请确保关闭文件的Scanner
。 -
您应该养成将块体包含在
{...}
中的习惯,即使体中只有一条语句。这将使您免于某些意外超出范围的语句,例如if (1 == 2) System.out.print("Hello"); System.out.println("World"); System.out.println("What's up?");
将打印
World
What's up?
而不仅仅是
What's up?
- 保持代码格式良好,因为这将帮助您轻松快速地找到问题。您的 IDE 可以通过单击按钮或按下组合键来格式化代码。
我更喜欢像 apache-commons-cli
这样的 cli-library