Question

当被要求'输入数字到decrpyt'时输入-2将结束while循环，然后打印结果2（解密的单词）。而是-2产生错误 'java.lang.StringIndexOutOfBoundsException：字符串索引超出范围：-2'

如何绕过这个？

import java.util.Scanner; 

public class Decrypt {

    public static void main(String[] args) {

        Scanner sc;
        int  result, input2, num, end = -2;
        String word, sourcetext, answer, encrypt = "1", decrypt="2";

        char input, result2;
        sc = new Scanner(System.in);

        System.out.println("please enter sourcetext");
        sourcetext = sc.nextLine();

        System.out.print("Would you like to 1: encrypt, or 2: decrypt?");
        answer = sc.next();

        System.out.println("please enter numbers to decrypt"); 
        while (answer.equals(decrypt)) {

            num = sc.nextInt();                   // number to decrypt
            result2 = sourcetext.charAt(num);     // num decrypted

            if (num <= end) {                     // int end = -2

                System.out.print(result2);

            }

        }
    }
}

Answer 1

当输入-2时，它会将其传递给charAt，这会引发异常，因为字符串中没有-2索引。您应该将if (num <= end)块移动到while循环的开头，并将其余块放入else块。

像这样：

if (num <= end){                     
    System.out.print(result2);
} else {
    num = sc.nextInt();                   // number to decrypt
    result2 = sourcetext.charAt(num);     // num decrypted
}

循环解密时出错

1 个答案: