提问人：codenaem 提问时间：11/21/2020 更新时间：11/21/2020 访问量：49
为什么这个 try 语句使用 catch 语句？[已结束]
Why does this try statement use the catch statement? [closed]
问：
import java.util.Scanner;
import java.util.InputMismatchException;
public class bank {
public static void login() {
double balance;
try {
boolean subtract;
boolean amounttaken;
// This is to see if you want to withdraw money
System.out.println("Do you want to withdraw money?");
Scanner SCaddOrWithdraw = new Scanner(System.in);
subtract = SCaddOrWithdraw.nextBoolean();
if (subtract) {
System.out.println("How much would you like to withdraw?");
Scanner SCamounttaken = new Scanner(System.in);
amounttaken = SCamounttaken.nextBoolean();
System.out.println("Subtract");
} else if (!subtract) {
System.out.print("Ask for bal");
}
} catch (InputMismatchException e) {
System.out.println("Invalid Input");
}
}
}
我添加了一个 try 语句，在 if 我告诉它打印减法的第一部分，但它调用了 catch 语句。有人可以帮忙吗？ 请记住，我是编码的初学者。
答：
1赞
Rehan Javed
11/21/2020
#1
这是一个完整的结构。
try {
// Statement Which May Throw Exceptions
} catch(Exception e) {
// If any statement throws the exception
// Do alternative flow here
}
如果 try 块中的代码可能会引发异常，则可以执行替代操作。就像在上面的代码中一样，如果有人输入一个字符串而不是布尔值，它将抛出 InputMismatchException，它将被捕获在 catch 块中，您可以漂亮而整齐地将错误消息打印给用户。:)
1赞
Arvind Kumar Avinash
11/21/2020
#2
您已声明 和 作为变量，因此它们只能采用或作为值，例如下面给出的是一个示例运行：subtractamounttakenbooleantruefalse
Do you want to withdraw money?
true
How much would you like to withdraw?
true
Subtract
如果尝试输入与 或 不同的值，则会得到 。truefalseInputMismatchException
我想你想为变量输入一些十进制数（金额）。如果是，则将其声明为 或代替，例如amounttakendoublefloatboolean
import java.util.InputMismatchException;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
login();
}
public static void login() {
double balance;
try {
boolean subtract;
double amounttaken;// Changed to double
// This is to see if you want to withdraw money
System.out.println("Do you want to withdraw money?");
Scanner SCaddOrWithdraw = new Scanner(System.in);
subtract = SCaddOrWithdraw.nextBoolean();
if (subtract) {
System.out.println("How much would you like to withdraw?");
Scanner SCamounttaken = new Scanner(System.in);
amounttaken = SCamounttaken.nextDouble();// Changed for double
System.out.println("Subtract");
} else if (!subtract) {
System.out.print("Ask for bal");
}
} catch (InputMismatchException e) {
System.out.println("Invalid Input");
}
}
}
示例运行：
Do you want to withdraw money?
true
How much would you like to withdraw?
3000
Subtract
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