扫描仪循环中断 + 正则表达式问题

Question

这个任务是一个单词是否是回文，我用的是java11.

输入带空格的单词后，代码会给出答案，但如果我选择 word = sc.next()，while 循环会中断并且代码“以退出代码 0 结束”。但是如果我写 word = sc.nextLine() - 它执行良好并再次开始循环。

我不明白为什么，因为我无法调试这部分代码，它只是被跳过了。而且我不明白为什么会这样。那么有人可以向我解释我做错了什么吗？

也许有办法避免这个空格？

P.S。我是编程新手。谢谢大家。

    try {

        Pattern pattern = Pattern.compile("[Y|y][E|e][S|s]");
       

        while (true) {
            String word = "";
            Scanner sc = new Scanner(System.in);
            System.out.println("Enter the word without spaces");

       

            if (sc.hasNext("(?>\p{Alpha})+")) {
                word = sc.next(); 
                System.out.println(word);
                System.out.println("The word is correct");
                String text2;
                StringBuilder sb = new StringBuilder();
                text2 =  sb.append(word).reverse().toString();

                if (word.equalsIgnoreCase(text2)) {
                    System.out.println("Yes, it's a palindrome." + " " + "Want to try another one?");
                    System.out.println("Enter yes if you want to continue" + " or " + "enter any symbol if no");
                    if (sc.hasNext(pattern)) {
                    }
                    else {
                        break;
                    }
                }

                else {
                    System.out.println("No, it's not a palindrome." + " " + "Want to try another one?");
                    System.out.println("Enter yes if you want to continue" + " or " + "enter any symbol if no");
                    if (sc.hasNext(pattern)) {
                    }
                    else {
                        break;
                    }
                }
            }

            else {
                word = sc.next();
                System.out.println("It's not a word");
                System.out.println("Want to try another one?");
                System.out.println("Enter yes if you want to continue" + " or " + "enter any symbol if no");
                if (sc.hasNext(pattern)) {
                }
                else {
                    break;
                }
            }
        }
    }

    catch (NoSuchElementException ex) {
        System.out.println(ex.getMessage());
    }

}

Answer 1

您可以在正则表达式中改进什么，[Y|y][E|e][S|s]？

改用[Yy][Ee][Ss]。 [] 指定一个字符 class 并且其中的所有字符都表示其中之一，即默认情况下它们带有隐式 OR。检查 this 以了解更多信息。

如何确定输入是否包含 space？

将" "传递给函数，String#contains确定它。

演示：

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            System.out.print("Enter a word without spaces: ");
            String word = sc.nextLine();
            if (word.contains(" ")) {
                System.out.println("It's not a word");
            } else {
                System.out.println("The word is correct");
                StringBuilder reverse = new StringBuilder(word).reverse();
                System.out.println(word.equalsIgnoreCase(reverse.toString()) ? "Palindrome" : "Not a palindrome");
            }
            System.out.println("Want to try another one?");
            System.out.print("Enter yes if you want to continue or any other symbol otherwise: ");
            if (!sc.nextLine().matches("[Yy][Ee][Ss]")) {
                break;
            }
        }
    }
}

样本运行:

Enter a word without spaces: Hello World
It's not a word
Want to try another one?
Enter yes if you want to continue or any other symbol otherwise: yes
Enter a word without spaces: HELLO
The word is correct
Not a palindrome
Want to try another one?
Enter yes if you want to continue or any other symbol otherwise: YES
Enter a word without spaces: Malayalam
The word is correct
Palindrome
Want to try another one?
Enter yes if you want to continue or any other symbol otherwise: Yes
Enter a word without spaces: papa
The word is correct
Not a palindrome
Want to try another one?
Enter yes if you want to continue or any other symbol otherwise: n