Question

每次运行这个程序时，我得到了错误的结果，我觉得额外的一双眼睛会在早上4点有用。有人可以帮我找到我的花括号或括号的位置，因为我找不到它的生命。

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

字符串应与.equals()方法进行比较，而不是==。

话虽如此，在您的情况下，您可能需要查看regular expressions，这样您就可以对输入进行 clean 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") ;
}

Answer 2

您需要将==更改为equals以比较String（和任何其他对象）的值。

你也遇到逻辑问题，因为userGuess != "a" || userGuess != "b"对所有字符都是正确的，因为如果有a，那么它不是b，所以其中一个条件将始终为真。

您可能希望将||更改为&&或使用正则表达式等适当的工具，或使用像Character.isLetter这样的Character类中的方法。

JAVA if语句逻辑或语法错误？

2 个答案: