如何在java中处理空的扫描仪输入字符串？

您可能想要使用。

 String furniID = reader.nextLine();
 furniID = furniID.trim();
 if(furniID.equals("")){
     System.out.println("Empty Here. ");
 }

正如评论中所建议的那样，如果您提供空行或直接按回车键，则返回一个空字符串。.readLine()

上面的正则表达式将处理空字符串或用户可能输入的字符串。""whitespaces

编辑 1正如评论中所建议的那样，正则表达式在这里可能有点矫枉过正。string.trim（） 将处理制表符、尾随前导空格和空字符串。

每当您提示用户提供特定数据时，您都应该验证输入的数据，如果数据不正确，请允许用户重试，以免由于某种可以避免的错误而停止应用程序。对于这种事情，使用正则表达式（正则表达式）是没有问题的。

用户不输入任何内容（只需按键）只是一个问题。在某些提示下，您期望用户仅输入数字。String#matches（） 方法中的小正则表达式是理想的选择，例如：ENTER

if (!userInput.matches("\\d+") {
   System.out.println("Invalid input! Numerical digits only!");
}

如果用户输入与所有数字不匹配，则显示“无效输入！

每个提示都应该在自己的 or 循环中，以便可以完成验证，并且用户有机会重新输入数据。如果您有很多提示，则可以创建一个类方法来处理所有这些提示，以删除重复的编码。例如，下面修改了您的代码，以便名为 askUser（） 的方法可以处理对用户的提示：dowhile

public class Generator {

    public static void main(String[] args) {
        java.util.Scanner reader = new java.util.Scanner(System.in);
        while (true) {
            // Only a String repesentation of numerical digits will be accepted. 
            // 1 to 20 digits are acceptable)
            String furniID = askUser(reader, "Input the furni ID (input only numbers here).", 
                    "\\d{1,20}");

            /* Only characters A to Z in either upper or lower case, digits 
               from 0 to 9, whitespaces, and underscores will be accepted 
               within the Users input. The period (.) is not acceptable 
               therefore eliminating the possibility of a file name extension
               like .swf to be applied to the supplied file name. File name can 
               be 1 to 80 characters.                               */
            String furniFileName = askUser(reader, "Input the furni's file name (without "
                    + "'.swf'.\nYou can input numbers, letters and underscores here).", 
                    "(?i)[a-z0-9 _]{1,80}");
            
            // Only a String repesentation of numerical digits will be accepted. 
            // 1 to 20 digits are acceptable)
            String furniRevision = askUser(reader, "Input the furni's revision (input "
                    + "only numbers here).", "\\d{1,20}");
            
            /* Only characters A to Z in either upper or lower case, digits 
               from 0 to 9, whitespaces, and underscores will be accepted 
               within the Users input. The period (.) is not acceptable. The
               name can be 1 to 25 characters in length.                  */
            String furniName = askUser(reader, "Input the furni's name (this will be "
                    + "the name that will\nbe displayed when you click on the furni in "
                    + "a room or in\nyour inventory).", "(?i)[a-z0-9 _]{1,25}");

            /* Only characters A to Z in either upper or lower case, digits 
               from 0 to 9, whitespaces, and periods will be accepted within 
               the Users input. Description can be a minimum of 5 to a maximum 
               of 120 characters in length.  */
            String furniDescription = askUser(reader, "Input the furni's description ("
                    + "this will be displayed\nunder the furni's name).", "(?i)[a-z0-9. ]{5,120}");

            /* Only characters A to Z in either upper or lower case, digits 
               from 0 to 9, and whitespaces will be accepted within the Users 
               input. The period (.) is not acceptable. The furniline name can 
               be 1 to 25 characters in length.                      */   
            String furniLine = askUser(reader, "Input the furni's furniline. This is just "
                    + "a name for a\ngroup of furnis that belong to the same collection. "
                    + "For\nexample you can input 'custom' (without quotation marks).", 
                    "(?i)[a-z0-9 ]{1,25}");

            System.out.println("Generating your furnidata...");
            System.out.println(" ");
            System.out.println("<furnitype id=\"" + furniID + "\"" + " classname=\"" + furniFileName + "\"" + ">");
            System.out.println("<revision>" + furniRevision + "</revision>");
            System.out.println("<xdim>1</xdim>");
            System.out.println("<ydim>1</ydim>");
            System.out.println("</partcolors>");
            System.out.println("<name>" + furniName + "</name>");
            System.out.println("<description>" + furniDescription + "</description>");
            System.out.println("</adurl");
            System.out.println("<offerid>-1</offerid>");
            System.out.println("<buyout>0</buyout>");
            System.out.println("<rentofferid>-1</rentofferid>");
            System.out.println("<rentbuyout>0</rentbuyout>");
            System.out.println("<bc>0</bc>");
            System.out.println("<excludeddynamic>0</excludeddynamic>");
            System.out.println("<customparams/>");
            System.out.println("<specialtype>1</specialtype>");
            System.out.println("<canstandon>0</canstandon>");
            System.out.println("<cansiton>0</cansiton>");
            System.out.println("<canlayon>0</canlayon>");
            System.out.println("<furniline>" + furniLine + "</furniline>");
            System.out.println("</furnitype>");
            System.out.println(" ");

            // Only y or n can be supplied in any letter case. 
            // Anything else generates an Invalid Input message.
            String confirmation = askUser(reader, "Do you want to generate another furnidata? (y/n)", 
                    "(?i)[yn]", "Invalid Choice! Either 'y' for Yes or 'n' for No!");
            if (confirmation.equalsIgnoreCase("n")) {
                System.out.println("Furnidata generator has been stopped.");
                break;
            }
        }
    }
    
    /**
     * Displays the supplied prompt within the Console Window and permits the User 
     * to enter a response. User input is validated based on the regex argument 
     * supplied to the <b>validationRegEx</b> parameter.<br><br>
     * 
     * @param inputReader (Scanner) Scanner object to use for User Input.<br>
     * 
     * @param promptString (String) The prompt to display within the console window.<br>
     * 
     * @param validationRegEx (String) A regular expression that will be used 
     * within a <b>String#matches()</b> method to validate the User's input.<br>
     * 
     * @param errorString (Optional - String) Default validation error message is:<pre>
     * 
     *     "Invalid input! Try again..."</pre><br>
     * 
     * Here you can optionally supply your own message for non-valid entries.<br>
     * 
     * @return (String) The valid response from User.
     */
    public static String askUser(java.util.Scanner inputReader, String promptString, String validationRegEx, String... errorString) {
        String userInput = "";
        String errString = "Invalid input! Try again...";
        if (errorString.length > 0 && !errorString[0].trim().isEmpty()) {
            errString = errorString[0];
        }
        
        while (userInput.isEmpty()) {
            System.out.println();
            System.out.println(promptString);
            userInput = inputReader.nextLine();
            if (!userInput.matches(validationRegEx)) {
                System.err.println(errString);
                userInput = "";
            }
        }
        return userInput;
    }
    
}