java - 读取整数并得到答案 + 10

Question

我编写了一个 readInt() 方法来从 System.in 读取整数，但由于某种原因，返回的每个整数都相差 10。无论数字是一位还是几位，这都让我感到困惑。我的代码如下，我哪里出错了？

/**
 * @return The next integer read from the Input Stream
 */
public static int readInt() throws IOException {
    BufferedInputStream in = new BufferedInputStream(System.in);
    char c = (char) in.read();
    int num = 0, cNum = Character.getNumericValue(c);

    //Checks that the current value of c is in fact a single digit number (as it must be to be a char and an int)
    while (cNum > -1 && cNum < 10) {
        num = num * 10 + cNum;

        c = (char) in.read();
        cNum = Character.getNumericValue(c);
    }

    //If no number has been read, keep reading until one is read
    if (num == 0 && c != '0') {
        return readInt();
    }

    System.out.print(num + '\n');
    return num;
}

示例 I/O:

输入(I):1 - 输出(O):11

我:2 - 奥:12

我:3 - 奥:13

我:5 - 奥:15

我:10 - 奥:20

我:99 - 奥:109

我:100 - 奥:110

Answer 1

当你将一个字符添加到一个整数时，它会进行整数运算。

所以

 x + '\n'

与

相同

 x + 10

因为 (int) '\n' 是 10

你想要的是

 x + "\n"

它进行字符串算术

但是更简单/更有效的解决方案是

 System.out.println(x);