Java Do-While 循環 - 如何使用 Q 選項結束程序
[英]Java Do-While Loop - How to End the Program Using Q Option
問題描述
所以我有這個簡單的銀行程序。 它的主菜單是：
- B - 檢查余額
- D - 存款
- W - 取款
- Q - 退出
他們的功能基本上就是他們的名字。 有兩種方法可以終止程序：輸入“Q”和“N”。但是我對 Q - Quit 選項有疑問。 這是源代碼：
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 output 是這樣的：
Welcome to ABC BANK
B - Check for Balance
D - Make Deposit
W - Make Withdraw
Q - Quit
Select an option :
當我輸入 Q 選項時，output 應該是這樣的：
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!
但是當我輸入它時，它會說這是一個無效輸入。 我應該怎么做才能通過輸入“Q”來結束程序？
2 個解決方案
解決方案1
2 2021-01-21 10:03:55
您的 Q 實現是正確的，它將退出 do while 循環，但是在 while 語句之后您有一個 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)");
}
當您鍵入 Q 退出循環時， anotherTransact不等於“N”，因此它將 go 放入 else 並打印無效條目。 如果我理解正確的話，在 while 語句之后你實際上不需要：
System.out.println("\n======================================================");
System.out.println("\nThank you for using this program!");
解決方案2
2 已采納 2021-01-21 19:52:53
您的代碼有兩個問題：
將以下代碼放在 scope 的
do-while循環之外：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，僅僅糾正這個問題是不夠的。 檢查下一個點/問題以了解需要做什么才能使其按您的期望工作。
在無效輸入的情況下不循環：你需要另一個循環（我推薦如下所示
do-while循環）來糾正這個問題。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);
完整的更新代碼：
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');
}
}
示例運行：
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!
一些附加說明：
您永遠不應該關閉
System.in的Scanner，因為它也會關閉System.in，並且如果不重新啟動 JVM 就無法再次打開它。但是，請確保關閉文件的Scanner。你應該養成將塊的主體包含在
{...}內的習慣，即使你在主體中只有一個語句。 這將使您免於意外掉出 scope 的某些語句，例如if (1 == 2) System.out.print("Hello"); System.out.println("World"); System.out.println("What's up?");
將打印
World
What's up?
而不僅僅是
What's up?
- 保持代碼格式正確，因為它可以幫助您輕松快速地找到問題。 您的 IDE 可以在單擊按鈕或按下組合鍵時格式化代碼。
解決方案3
-2 2021-01-21 09:57:08
所以我有這個簡單的銀行程序。 它的主菜單是：
- B - 檢查余額
- D - 存款
- W - 取款
- Q - 退出
它們的功能基本上就是它們的名字。 並且有兩種方法可以終止程序：通過輸入“Q”和“N”。但我對 Q - Quit 選項有疑問。 這是源代碼：
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 output 是這樣的：
Welcome to ABC BANK
B - Check for Balance
D - Make Deposit
W - Make Withdraw
Q - Quit
Select an option :
當我輸入 Q 選項時，output 應該是這樣的：
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!
但是當我輸入它時，它會說它是一個無效的輸入。 我應該怎么做才能通過輸入“Q”來結束程序？
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