逻辑错误导致语句在While循环中打印两次

Question

因此，我当前遇到的问题是，在我完成所有步骤后，“Enter your command（reverse,replace first,replace last,remove all,remove）”语句被打印了两次。

我相信正在发生的是循环执行了两次，但我不知道为什么。如果能帮助解决这个问题，我们将不胜感激。抱歉，如果我的代码格式不好，还在学习如何正确的格式。

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

处理完一个字符后会得到两个条目的原因是您没有完全阅读包含该字符的行。

具体而言，在上分支中使用Keyboard.NextInt()；，在下分支中使用Keyboard.Next()；。当它们分别读取下一个整数和字符时，它们不处理行尾标记。

然后，当您到达循环的顶部时，您调用keyboard.nextLine()，它处理int（或字符，在remove all大小写中）之后出现的任何字符，直到行结束标记。对于预期的用户输入，这只是一个空字符串。

要解决这一问题，您需要确保在只读取整数或单个字符的情况下，您能够读取键盘。nextLine()。