英文:
if branches within while loop not executing as expected
问题
这是我正在使用的代码。这里引用的其他类已经经过测试并且有效，尽管它们不应该影响这里的语句的功能。
import java.util.Scanner;
public class TransferTest
{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
double transferAmount;
Account acct1 = new Account(100, null);
Account acct2 = new Account(100, null);
System.out.print("选择一个选项："
+ "\n1 <Enter>: 从帐户1转帐到帐户2"
+ "\n2 <Enter>: 从帐户2转帐到帐户1"
+ "\n3 <Enter>: 退出");
int userOption = scan.nextInt();
scan.nextLine();
while(userOption != 3);
{
if (userOption == 1)
{
System.out.print("您选择了从帐户1转帐到帐户2"
+ "\n输入要转帐的金额：");
transferAmount = scan.nextInt();
acct1.transfer(acct2, transferAmount);
}
else if (userOption == 2)
{
System.out.print("您选择了从帐户2转帐到帐户1"
+ "\n输入要转帐的金额：");
transferAmount = scan.nextInt();
acct2.transfer(acct1, transferAmount);
}
else if (userOption == 3)
{
System.out.println(acct1.toString());
System.out.println(acct2.toString());
}
else
{
System.out.println("无效的输入");
}
System.out.print("选择一个选项："
+ "\n1 <Enter> 从帐户1转帐到帐户2？"
+ "\n2 <Enter> 从帐户2转帐到帐户1"
+ "\n3 <Enter> 退出");
userOption = scan.nextInt();
scan.nextLine();
}
System.out.println(acct1.toString());
System.out.println(acct2.toString());
scan.close();
}
}
我想要它做的是提示用户选择由数字值表示的三个选项之一。然后根据该值的条件分支，如果是1或2，则要求用户输入金额。只有当用户选择选项3时才退出while循环。发生的情况是，当输入3或指定范围之外的值时，程序按预期工作，但当选择1或2作为选项时，什么都不会发生，甚至不会输出打印语句。非常感谢您帮助我解决这个问题。
英文:
Here is the code that I am working with. The other classes that are referenced here have been tested and work though they should not have an effect on the functionality of the statements here.
import java.util.Scanner;
public class TransferTest
{
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
double transferAmount;
Account acct1 = new Account(100, null);
Account acct2 = new Account(100, null);
System.out.print("Choose an option: "
+ "\n1 <Enter>: to transfer from account 1 to account 2"
+ "\n2 <Enter>: to transfer from account 2 to account 1"
+ "\n3 <Enter>: to quit");
int userOption = scan.nextInt();
scan.nextLine();
while(userOption != 3);
{
if (userOption == 1)
{
System.out.print("You chose transfer from account 1 to account 2"
+ "\nEnter an amount to transfer: ");
transferAmount = scan.nextInt();
acct1.transfer(acct2, transferAmount);
}
else if (userOption == 2)
{
System.out.print("You chose transfer from account 1 to account 2"
+ "\nEnter an amount to transfer: ");
transferAmount = scan.nextInt();
acct2.transfer(acct1, transferAmount);
}
else if (userOption == 3)
{
System.out.println(acct1.toString());
System.out.println(acct2.toString());
}
else
{
System.out.println("Invalid input");
}
System.out.print("Choose an option: "
+ "\n1 <Enter> to transfer from account 1 to account 2?"
+ "\n2 <Enter> to transfer from account 2 to account 1"
+ "\n3 <Enter> to quit");
userOption = scan.nextInt();
scan.nextLine();
}
System.out.println(acct1.toString());
System.out.println(acct2.toString());
scan.close();
}
}
What I'm wanting this to do is prompt a user to choose one of the three options denoted by a numerical value. Then follow the if branch of that value, asking the user for an amount in the case of 1 or 2. Not exiting the while loop until the user chooses option 3. Whats happening is that when 3 or a value outside the specified range is entered the program works as expected, but when 1 or 2 are chosen as options nothing happens, not even the print statements are output. Any help with getting this working is much appreciated.
答案1
得分: 5
你的 while 循环后面有一个分号。
while(userOption != 3);
等效于：
while(userOption != 3) {
// 什么都不做
}
因此，在该行之后的代码都不会被执行。
英文:
You have a semi-colon after your while loop.
while(userOption != 3);
Is effectively equal to:
while(userOption != 3) {
// do nothing
}
So no code after that line is being executed.
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