java中的输入错误

当给定输入与预期输入格式不匹配时

Exception in thread "main" java.util.InputMismatchException
	at java.base/java.util.Scanner.throwFor(Scanner.java:939)
	at java.base/java.util.Scanner.next(Scanner.java:1594)
	at java.base/java.util.Scanner.nextInt(Scanner.java:2258)
	at java.base/java.util.Scanner.nextInt(Scanner.java:2212)
	at calculator01.main(calculator01.java:10)

Process finished with exit code 1

检查输入是否和要求的输入格式相同

例`使用java制作简易计算器时，根据代码要求，需要的输入是“5 + 3”这种而不是“5+3” ，注意空格

public static void main(String[] args) {

    Scanner scanner = new Scanner(System.in);
    System.out.println("请输入算术");
    
       int a = scanner.nextInt();

       char signal = scanner.next().charAt(0);

       int b = scanner.nextInt();
    switch (signal) {
        case'+':plus(a,b);break;
        case'-':subtract(a,b);break;
        case'*':multiply(a,b);break;
        case'/':expect(a,b);break;
    }
    scanner.close();
}

private static void plus(int a,int b) {
    System.out.println(a+b);
    }
private static void subtract(int a,int b){
    System.out.println(a-b);
    }
private static void multiply(int a,int b){
    System.out.println(a*b);
}
private static void expect(int a,int b){
    System.out.println(a/b);
}

}
`