尝试使用 Integer.parseInt() 将字符串转换为整数时出错

Question

***更新我的帖子以显示我的所有代码，希望这提供更多上下文。

当我运行该程序时，它会跳过我的第一个“if”语句并抛出错误。***

我收到错误Exception in thread "main" java.lang.NumberFormatException: For input string: ""

我正在尝试在 while 循环的第一个 else 语句中将字符串变量转换为 int...错误发生在int examScore = Integer.parseInt(userInput).

   import java.util.Scanner;//imports scanner

   public class ExamScoresCalculator{

   public static void main(String[] args){

   Scanner scan = new Scanner(System.in);//creates new scanner object 

   //prompts user for lowest possible exam score

   System.out.println("Enter the lowest possible value for the exam: ");

   int lowRange = scan.nextInt();

   //prompts user for highest possible exam score

   System.out.println("Enter the highest possible value for the exam: ");

   int highRange = scan.nextInt();

   boolean flag = true; //while loop flag

   double lowestExamScore = highRange; // holds lowest score

   double highestExamScore = lowRange; //holds highest score

   double totalPoints = 0; //holds sum of all scores entered

   int totalExams = 0; //holds the total number of exams entered by the user

   while (flag == true){

      System.out.println("Enter an exam score between " + lowRange + " and " + highRange + " or type exit. "); //asks user for an exam score within correct range     

      String userInput = scan.nextLine();

      if ((userInput.equals("exit")) || (userInput.equals("Exit")) || (userInput.equals("EXIT"))){ //checks if user enters "exit"

         flag = false; //ends while loop

      }

Answer 1

一旦您按ENTER输入最高分数，扫描仪就会读取整数（nextInt），但也会读取行尾（nextLine）。由于该行中没有提供文本，因此它被读取为空字符串“”。您应该在代码中将scanner.nextInt替换为scanner.nextLine。它应该可以在以下更改中正常工作。//prompts user for lowest possible exam score  System.out.println("Enter the lowest possible value for the exam: ");   int lowRange = Integer.parseInt(scan.nextLine());   //prompts user for highest possible exam scoreSystem.out.println("Enter the highest possible value for the exam: ");   int highRange = Integer.parseInt(scan.nextLine());

Answer 2

请使用userInput和 的两个输入examScore，这将解决您的问题，因为您不能对String和Integer数据类型使用单个值。（但当您的输入值为“123”（仅限数字）时，这是可能的，即使这也不适用于您的程序）

Answer 3

添加 scan.nextLine() 来移动扫描仪以读取下一行（新行）。System.out.println("Enter the highest possible value for the exam: ");int highRange = scan.nextInt();scan.nextLine();   // Add this line