java - Java 中的 char 算术

Question

我编写了下面的代码，将小写转换为大写，将大写转换为小写，但它无法正常运行。此代码触发以下错误:

Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
    Type mismatch: cannot convert from int to char
    Type mismatch: cannot convert from int to char
    at learn.Example.main(Example.java:20)

<小时/>

public class Example 
{
    public static void main(String args[])
    throws java.io.IOException
    {
        char ch;

        System.out.println("Enter an alphabet only: ");

        do
        {
            ch = (char) System.in.read();

            if (ch>='a' & ch <= 'z')
            {
                ch= ch-32;
                System.out.println(ch);
            }
            if (ch >='A' & ch <= 'Z')
            {
                ch = ch + 32;
                System.out.println(ch);
            }
        }
        while (ch != '.');
    }
}

Answer 1

改变

ch = ch - 32;

至

ch = (char) (ch - 32);

因为该算术运算符的结果是 int 并且必须显式转换为 char。

同样改变

ch = ch + 32;

至

ch = (char) (ch + 32);