Java程序無法編譯

Question

我正在jgrasp下制作此程序，但出現錯誤。 我檢查了程序的拼寫和語法，這似乎是正確的。 請幫助我-我缺少某些東西導致我所有的錯誤嗎？

import javax.swing.*;


public class Testscore
{
   public static void main(String[] args) 
    {
       int numberofTests = 0;

       double grade = new double[numberofTests];

       double startgrade = 0;

        int x = 1 ;

       String strInput;

    // Get how many tests are used

       strInput = JOptionPane.showInputDialog(null, "How many tests do you have? ");
       numberofTests = Integer.parseInt(strInput);

       grade = new double[(int) numberofTests];
         do

         {

       for (int index = 0; index < grade.length; index++)
       {
           strInput = JOptionPane.showInputDialog(null, "Enter Test Score." + (index + 1));
           grade = Double.parseDouble(strInput);

           if (grade[index] < 0 || grade[index] > 100 )
           {   
               try 
                {
                   throw new InvalidTestScore();
                    x=2;
                }

               catch (InvalidTestScore e)
               {
                   e.printlnStackTrace();
                    system.out.println ("Choose a test score between 0 and 100");
               }
           }   
       }
       }
         while (x==1);

       for (int index = 0; index < grade.length; index++ )

            {
                startgrade += grade[index];
            }

            average = startgrade/grade.length;

            System.out.print("The average is: " + average);

    }
}

這是我遇到的錯誤。

Testscore.java:12: incompatible types

found   : double[]

required: double

       double grade = new double[numberofTests];

                      ^
Testscore.java:25: incompatible types

found   : double[]

required: double

       grade = new double[(int) numberofTests];

               ^
Testscore.java:30: double cannot be dereferenced

       for (int index = 0; index < grade.length; index++)
                                        ^
Testscore.java:35: array required, but double found

           if (grade[index] < 0 || grade[index] > 100 )
                    ^
Testscore.java:35: array required, but double found

           if (grade[index] < 0 || grade[index] > 100 )
                                        ^
Testscore.java:39: cannot find symbol
symbol  : class InvalidTestScore
location: class Testscore
                   throw new InvalidTestScore();
                             ^
Testscore.java:43: cannot find symbol

symbol  : class InvalidTestScore

location: class Testscore

               catch (InvalidTestScore e)
                      ^
Testscore.java:46: package system does not exist

                    system.out.println ("Choose a test score between 0 

and 100");
                          ^
Testscore.java:53: double cannot be dereferenced

       for (int index = 0; index < grade.length; index++ )
                                        ^
Testscore.java:56: array required, but double found

                startgrade += grade[index];

     ^
Testscore.java:59: cannot find symbol

symbol  : variable average

location: class Testscore

            average = startgrade/grade.length;
            ^
Testscore.java:59: double cannot be dereferenced

            average = startgrade/grade.length;
                                      ^
Testscore.java:61: cannot find symbol

symbol  : variable average

location: class Testscore

            System.out.print("The average is: " + average);
                                                  ^
13 errors

Answer 1

在第12行，嘗試更改

double grade = new double[numberofTests];

至

double[] grade = new double[numberofTests];

所有隨后的錯誤似乎都是編譯器認為grade是double精度而不是數組的結果。 例如，提到“解引用”是指索引到數組中； 索引成標量double不合理的。

Answer 2

編譯器非常有用，它會告訴您錯誤所在的行以及錯誤所在。

第一個錯誤在第12行，告訴您已將數組引用分配給非數組對象，應更改

 double grade = new double[numberofTests];

至

double grade[] = new double[numberofTests];

第25行上的下一個類似。 接下來的3個錯誤是由於前兩個錯誤，因為您將grade聲明為double，但稍后嘗試將其用作數組。

第39行Testscore.java:39: cannot find symbol symbol : class InvalidTestScore上的錯誤Testscore.java:39: cannot find symbol symbol : class InvalidTestScore意味着編譯器找不到您的InvalidTestScore類-它在哪里？ 您也應該編譯該類。

第46行的錯誤是system.out.println應該是System.out.println （System中的大寫S）

第59行的錯誤表明沒有名為average變量。您可以將其定義為存在的表達式的結果，因此只需更改average = startgrade/grade.length; double average = startgrade/grade.length;