無法評估用戶輸入

Question

所以我一直在研究這個Java程序，在這個程序中，計算機詢問用戶他是否想知道數字的平方。如果用戶的答案是'Y'或'y'，計算機會向用戶詢問他想要的數字，並且想知道數字的平方，並打印數字的平方。然後計算機詢問用戶他是否想知道另一個數字的正方形。如果答案是'Y'或'y'，則計算機會記錄一個數字並打印出正方形。再次詢問用戶他是否想知道另一個數字的平方。像這樣繼續。

我也寫過代碼的情況下，用戶的答案是否定的，或既不積極也不消極。通過這個，我的意思是用戶的答案是'N'或'n'的情況。這個程序在某個地方遇到問題，並且不按照我希望的方式從A到Z工作。看，當我運行代碼時，計算機問我是否想知道數字的平方，然後輸入'y'。然後我被問到我想知道的平方數。我輸入數字，電腦打印出它的正方形。然後我被問到是否想知道另一個數字的平方。我輸入'y'。然後我被問到我想知道廣場的數字，然後輸入一個數字。計算機打印數字的平方。然後該程序詢問我是否想知道另一個數字的正方形，並且只是結束，而本來應該回答我的答案。我已經工作了將近16到17個小時，試圖找到這個錯誤，但是我不能。你可以請測試代碼並告訴我哪裏出了錯？謝謝。

這是代碼：

package looppracticea; 

import java.util.Scanner; 

public class LoopPracticeA { 

    public static void main(String[] args) { 

     Scanner geek = new Scanner(System.in); 
     Scanner geek2 = new Scanner(System.in); 

     long taken_number, taken_number2; 
     String answer, answer2, answer_not_recognized, if_answer_is_no; 
     answer_not_recognized = "You didn't enter any of the recognized answers."; 
     if_answer_is_no = "'Kay. Whatever."; 

     System.out.println("Do you want to know the square of a number? (Y/N)"); 
     answer = geek.nextLine(); 

     if (answer.equals("Y") || answer.equals("y")) { 
      System.out.println("The number you want to know the square of is:"); 
      taken_number = geek.nextLong(); 
      System.out.println("That number squared is " + taken_number * taken_number + "."); 
      System.out.println("Do you want to know the square of another number? (Y/N)"); 
      answer2 = geek2.nextLine(); 

      switch (answer2) { 
       case "N": 
        System.out.println(if_answer_is_no); 
        break; 
       case "n": 
        System.out.println(if_answer_is_no); 
        break; 

       case "Y": 
        while (answer2.equals("Y")) { 
          System.out.println("The number you want to know the square of is:"); 
          taken_number2 = geek2.nextLong(); 
          System.out.println("That number squared is " + taken_number2 * taken_number2 + "."); 
          System.out.println("Do you want to know the square of another number? (Y/N)"); 
          answer2 = geek2.nextLine(); 
        } 
       break; 

       case "y": 
        while (answer2.equals("y")) { 
          System.out.println("The number you want to know the square of is:"); 
          taken_number2 = geek2.nextLong(); 
          System.out.println("That number squared is " + taken_number2 * taken_number2 + "."); 
          System.out.println("Do you want to know the square of another number? (Y/N)"); 
          answer2 = geek2.nextLine(); 
        } 
       break; 

       default: 
        System.out.println(answer_not_recognized); 
        break; 
      } 


     } else if (answer.equals("N") || answer.equals("n")) { 
      System.out.println(if_answer_is_no); 
     } else { 
      System.out.println(); 
      System.out.println(answer_not_recognized); 
     } 

    } 

} 

Answer 1

這裏是你的主要的固定內容：

 Scanner geek = new Scanner(System.in); 

     long taken_number; 
     String answer; 
     String answer_not_recognized = "You didn't enter any of the recognized answers."; 
     String if_answer_is_no = "'Kay. Whatever."; 
     boolean firstTime = true; 

     while(true) 
     { 
      if(firstTime) 
       System.out.println("Do you want to know the square of a number? (Y/N)"); 
      else 
       System.out.println("Do you want to know the square of another number? (Y/N)"); 
      answer = geek.nextLine(); 
      if (answer.equalsIgnoreCase("y")) 
      { 
       System.out.println("The number you want to know the square of is:"); 
       taken_number = geek.nextLong(); 
       System.out.println("That number squared is " + taken_number * taken_number + "."); 
       answer = geek.nextLine(); 
      } 
      else if (answer.equalsIgnoreCase("n")) { 
       System.out.println(if_answer_is_no); 
       break; 
      } else { 
       System.out.println(); 
       System.out.println(answer_not_recognized); 
       break; 
      } 
      if(firstTime) 
       firstTime = false; 
     } 

的問題是，你必須讀取的行兩次，以獲得您想要的線。
第一個nextLine將讀取輸入

另外我減少的代碼：

• 只留下一個Scanner因爲這是足夠
• 使用equalsIgnoreCase代替2- equals
• 用過只有一個answer和taken_number變量，因爲那已經足夠了
• 將變量聲明放在單獨的行上，因爲它更容易維護一個約定。
• 將兩個輸入讀數合併爲一個，用布爾值告訴我是否是第一次，所以我知道要輸出什麼消息。
• 閱讀nextLine() 2次，因爲第一個是進入