我在其他项目中也遇到过几次这个问题。现在我尝试了解异常处理,但我仍然不知道它到底是如何工作的。 我尝试用循环编写一个计算器,当我尝试输入一个字符串时,会出现InputMismatchException - 我试图捕获它,但由于某种原因,在catch子句之后,java给了我另一个InputMismatchException,为什么?
import java.util.InputMismatchException;
import java.util.Scanner;
public class Calculator {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int loop = 1;
while (loop == 1) {
try {
System.out.println("First number:");
int num1 = scanner.nextInt();
System.out.println("Second number:");
int num2 = scanner.nextInt();
System.out.println("Choose operator (1 for +)(2 for -)(3 for *)(4 for /): ");
int userInput = scanner.nextInt();
switch (userInput) {
case 1:
System.out.println("Result: " + num1 + " + " + num2 + " = " + (num1 + num2));
break;
case 2:
System.out.println("Result: " + num1 + " - " + num2 + " = " + (num1 - num2));
break;
case 3:
System.out.println("Result: " + num1 + " * " + num2 + " = " + (num1 * num2));
break;
case 4:
System.out.println("Result: " + num1 + " / " + num2 + " = " + (num1 / num2));
break;
default:
System.out.println("Invalid Input!");
}
System.out.println("Repeat? (1 = yes)(0 = nein)");
loop = scanner.nextInt();
} catch (InputMismatchException e) {
System.out.println("Invalid Input, try again!");
scanner.nextInt();
}
}
scanner.close();
System.out.println("Ciao!");
}
}
起初有一个无限循环,我通过 catch block 中的 scanner.nextInt();
解决了这个问题,但我仍然收到此错误:
Choose operator (1 for +)(2 for -)(3 for *)(4 for /):
er
Invalid Input, try again!
Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at Calculator.main(Calculator.java:47)
为什么?
最佳答案
可能是因为您没有获取 nextInt,因为下一个值不是 int
。因此,您尝试在 catch block 中再次获取相同的输入,从而再次出现 InputMismatchException。
您的 Stacktrace 还指向您尝试检索下一个 int
的 catch 子句!
我建议您将 catch 子句中的 nextInt
替换为 nextLine
:
...
catch (InputMismatchException e) {
System.out.println("Invalid Input, try again!");
scanner.nextLine();
}
然后您将再次开始循环并尝试重新阅读。
还结帐this stackoverflow 或 tutorialspoint examples for using the Scanner
class 上的类似线程.
关于java - 关于循环内异常(try-catch)的问题,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/58816560/