JAVA if 语句逻辑或语法错误？

Question

这个问题已经有答案了:

How do I compare strings in Java? (23 个回答)

已关闭 9 年前。

每次运行这个程序时，我都会得到错误的结果，我觉得在凌晨 4 点多一双眼睛会有所帮助。有人可以帮我找到我的大括号或括号的位置吗，因为我一辈子都找不到它。

System.out.println("Please enter your guess") ;
    userGuess = kbd.next() ;
    if( userGuess != "a" || userGuess != "b" || userGuess != "c" || 
        userGuess != "d" || userGuess != "e" || userGuess != "f" || userGuess != "g" ||
        userGuess != "h" || userGuess != "i" || userGuess != "j" || userGuess != "k" ||
        userGuess != "l" || userGuess != "m" || userGuess != "n" || userGuess != "o" || 
        userGuess != "p" || userGuess != "q" || userGuess != "r" || userGuess != "s" || 
        userGuess != "t" || userGuess != "u" || userGuess != "v" || userGuess != "w" || 
        userGuess != "x" || userGuess != "y" || userGuess != "z" ||  userGuess!= "A" || 
        userGuess != "B" || userGuess != "C" || userGuess != "D" || userGuess != "E" || 
        userGuess != "F" || userGuess != "G" ||userGuess  != "H" || userGuess != "I" || 
        userGuess != "J" || userGuess != "K" ||userGuess  != "L" || userGuess != "M" || 
        userGuess != "N" || userGuess != "O" || userGuess != "P" || userGuess != "Q" || 
        userGuess != "R" || userGuess != "S" || userGuess != "T" || userGuess != "U" || 
        userGuess != "V" || userGuess != "W" || userGuess != "X" || userGuess != "Y" || 
        userGuess != "Z" ) {
        System.out.println("Invalid character, please enter your guess") ;
    }userGuess = kbd.next() ;

Answer 1

字符串应该与 .equals() 方法进行比较，而不是 ==。

话虽如此，在您的情况下，您可能想看看 regular expressions ，这将允许您对输入进行干净验证。简而言之:

//This code is untested, but it should guide you to what you need to do
Pattern userInput = Pattern.compile("^[A-Za-z]$");   //A-Z will match all the characters ranging from A to Z. a-z will do the same but it will check the lower case range. Alternatively, you could use ^[a-z]/i$ to make your regular expression case insensitive.
Scanner kbd = new Scanner(System.in);
String input = kbd.next();
Matcher matcher = userInput.matcher(input);
if(!matcher.matches())
{
    System.out.println("Invalid character, please enter your guess") ;
}