除非你非常渴望表现，否则我会采用一种非常简单的方法：

Unless you're absolutely desperate for performance, I'd use a very simple approach:

String result = input.replace("*", "asterisk")
                     .replace("%", "percentage")
                     .replace("@", "at"); // Add more to taste :)

（请注意，替换和 replaceAll - 后者采用正则表达式。很容易得到错误的并看到截然不同的效果！）

(Note that there's a big difference between replace and replaceAll - the latter takes a regular expression. It's easy to get the wrong one and see radically different effects!)

另一种选择是：

public static String replaceSpecial(String input)
{
    // Output will be at least as long as input
    StringBuilder builder = new StringBuilder(input.length());

    for (int i = 0; i < input.length(); i++)
    {
        char c = input.charAt(i);
        switch (c)
        {
            case '*': builder.append("asterisk"); break;
            case '%': builder.append("percentage"); break;
            case '@': builder.append("at"); break;
            default: builder.append(c); break;
        }
    }
    return builder.toString();