java - 逻辑错误导致语句在 While 循环中打印两次

Question

所以我当前遇到的问题是，在我完成所有步骤后，语句“输入您的命令(反向，首先替换，最后替换，全部删除，删除)”打印了两次。

我相信正在发生的是循环执行了两次，但我不知道为什么。任何帮助解决这个问题将不胜感激。如果我的代码格式不好，请提前抱歉，仍在学习如何正确格式化。

import java.util.Scanner;

public class StringChangerenter {
    public static void main(String[] args) {
        Scanner keyboard = new Scanner(System.in);
        // Output Variables
        String userInput = "";

        // Variables
        String removeChar = "", removeAllChar = "";
        int removeIndex = 0;

        // First Output
        System.out.println("Enter the string to be manipulated");
        userInput = keyboard.nextLine();
        String command = "";

        // While loop
        while (!command.equalsIgnoreCase("quit")) {
            // Output
            System.out.println("Enter your command (reverse, replace first, replace last, remove all, remove)");
            command = keyboard.nextLine();
            if (command.equalsIgnoreCase("remove")) {
                System.out.println("Enter the character to remove");
                removeChar = keyboard.nextLine();
                int totalCount = 0;
                for (int j = 0; j < userInput.length(); j++) {
                    if (userInput.charAt(j) == removeChar.charAt(0)) {
                        totalCount = totalCount + 1;
                    }
                }
                System.out.println("Enter the " + removeChar
                        + " you would like to remove (Not the index - 1 = 1st, 2 = 2nd, etc.):");
                removeIndex = keyboard.nextInt();
                int currentIndex = 1;
                if (removeIndex <= totalCount) {
                    for (int i = 0; i < userInput.length(); i++) {
                        if (userInput.charAt(i) == removeChar.charAt(0)) {
                            if (currentIndex == removeIndex) {
                                String firstpartOfString = userInput.substring(0, i);
                                String secondpartOfString = userInput.substring(i + 1, userInput.length());
                                System.out.println("The new sentence is " + firstpartOfString + secondpartOfString);
                                userInput = firstpartOfString + secondpartOfString;
                                break;
                            } else {
                                currentIndex = currentIndex + 1;
                            }
                        }
                    }
                } else {
                    System.out.println("Can't find " + removeChar + " occuring at " + removeIndex + " int the string.");
                }
                // Remove All Code

            } else if (command.equalsIgnoreCase("remove all")) {
                System.out.println("Enter the character to remove");
                removeAllChar = keyboard.next();
                String newString = "";
                for (int i = 0; i < userInput.length(); i++) {
                    if (userInput.charAt(i) != removeAllChar.charAt(0)) {
                        newString = newString + userInput.charAt(i);
                    }
                }
                userInput = newString;
                System.out.println("The new sentence is " + userInput);
            }
            // Bracket for while loop
        }
    }
}

Answer 1

处理完一个字符后，您收到两个条目的原因是您尚未完全阅读包含该字符的行。

具体来说，您在上部分支中使用 keyboard.nextInt(); ，在下部分支中使用 keyboard.next(); 。虽然它们分别读取下一个整数和字符，但它们不处理行尾标记。

然后，当到达循环顶部时，调用 keyboard.nextLine() 来处理 int (或字符，在删除所有情况下)之后出现的任何字符，直到行尾标记。对于预期的用户输入，这只是一个空字符串。

要解决此问题，您需要确保在仅读取整数或单个字符的情况下完整读取 keyboard.nextLine()。