运行此代码时出现问题，我收到了 a.class 错误

Question

I'm having issues getting this to run.

I can't manage to get the return value to work properly. I'm a few weeks into this course and I'm learning a lot but this project has been a little bit of a struggle for me.

I'm collecting data, creating an average and then using that average to output the corresponding letter grade.

Any help would be appreciated.

   import java.util.*;
    public class LetterGrade
    {
       public static void main(String args[]) 
       {
         calculateAvg();
         double avgScore;
         printLetter(double);


        }
        public static void calculateAvg()
           {      
              Scanner console = new Scanner(System.in);
              double avgScore; 

          for (double i = 0; i >0; i++) 
          {
              System.out.println("Enter your full name.");
              String name = console.nextLine();
              System.out.println("Enter test score 1");
              double score1 = console.nextDouble();
              System.out.println("Enter test score 2");
              double score2 = console.nextDouble();
              System.out.println("Enter test score 3");
              double score3 = console.nextDouble();

              avgScore = (score1 + score2 + score3) / 3;
              avgScore = console.nextInt();

              System.out.printf( "%s, your average test score is: %.1f",name,avgScore);

                return avgScore;
              }
         }

            public static void printLetter(double avgScore)
            {
                    Scanner console = new Scanner(System.in);
                    char grade;

                 if (avgScore >= 90)
                 {
                      grade = 'A';
                  }
                  else if (avgScore >= 80)
                  {
                     grade = 'B';
                  }
                  else if (avgScore >= 70)
                  {
                     grade = 'C';
                  }
                  else if (avgScore >= 60)
                  {
                     grade = 'D';
                  }
                  else
                  {
                     grade = 'F';
                 }

                    System.out.println("With that average, your grade is: " + grade);

       }
    }

Answer 1

There are several errors in your program.

I have corrected the program with comments:

import java.util.*;
public class LetterGrade
{
    public static void main(String args[]) 
    {

        double avgScore=  calculateAvg();
        printLetter(avgScore); //pass variable name here not datatype


    }
    public static double calculateAvg() //must have return type
    {      
        Scanner console = new Scanner(System.in);
        double avgScore; 

        // for (double i = 0; i 0; i++) 
        //{
        System.out.println("Enter your full name.");
        String name = console.nextLine();
        System.out.println("Enter test score 1");
        double score1 = console.nextDouble();
        System.out.println("Enter test score 2");
        double score2 = console.nextDouble();
        System.out.println("Enter test score 3");
        double score3 = console.nextDouble();

        avgScore = (score1 + score2 + score3) / 3;
        // avgScore = console.nextInt();

        System.out.printf( "%s, your average test score is: %.1f",name,avgScore);

        return avgScore;
        // }
    }

    public static void printLetter(double avgScore)
    {
        //Scanner console = new Scanner(System.in);
        char grade;

        if (avgScore >= 90)
        {
            grade = 'A';
        }
        else if (avgScore >= 80)
        {
            grade = 'B';
        }
        else if (avgScore >= 70)
        {
            grade = 'C';
        }
        else if (avgScore >= 60)
        {
            grade = 'D';
        }
        else
        {
            grade = 'F';
        }

        System.out.println("With that average, your grade is: " + grade);

    }
}

OUTPUT:
Enter your full name. manisha Enter test score 1 12 Enter test score 2 14 Enter test score 3 15 manisha, your average test score is: 13.7With that average, your grade is: F

Answer 2

Checkout your main function. You have to assign the variable correctly to the return value of the calculateAvg method. Try this out:

public static void main(String args[]) {

    double avgScore = calculateAvg();
    printLetter(avgScore);

}

Also notice: double is the type of the variable, not the name. You have to give the name into the printLetter() method.

Another issue I just found is the doubled assigning of the avgScore variable which you have in your calculateAvg() method. Remove this line:

avgScore = console.nextInt();

This would force the user to again type in a value, which gets then assigned to the variable avgScore. This is not necessary.

Answer 3

There are some comments that I hope to be useful for you: 1- change the code in the main method to be like that double avgScore = calculateAvg(); printLetter(avgScore); double avgScore = calculateAvg(); printLetter(avgScore); 2- check the use of the for loop (maybe you need a do while loop) 3- remove the scanner in "printLetter" method 4- also as @NiklasLehnfeld suggest to remove avgscore = console.nextInt();

Answer 4

You made many mistakes.

In the main method you should save the calculated average into the variable and pass it to the printLetter method like this

double avgScore = calculateAvg();
printLetter(avgScore);

The calculateAvg method return type should be double so you have to declare it like this

public static double calculateAvg()

Also the for loop inside calculateAvg is wrong and unnecessary so just remove it. And assigning the scanner.nextInt() value to the avgScore will discard the properly calculated value. so the calculateAvg method should be like this

The printLetter method is correct but contains unnecessary lines like

Scanner console = new Scanner(System.in); //Could be removed

The resulting code is

import java.util.*;

public class LetterGrade
{
    public static void main(String args[])
    {
        double avgScore = calculateAvg();
        printLetter(avgScore);
    }

    public static double calculateAvg()
    {
        Scanner console = new Scanner(System.in);
        double avgScore;

        System.out.println("Enter your full name.");
        String name = console.nextLine();
        System.out.println("Enter test score 1");
        double score1 = console.nextDouble();
        System.out.println("Enter test score 2");
        double score2 = console.nextDouble();
        System.out.println("Enter test score 3");
        double score3 = console.nextDouble();

        avgScore = (score1 + score2 + score3) / 3;

        System.out.printf( "%s, your average test score is: %.1f\n", name, avgScore);

        return avgScore;
    }

    public static void printLetter(double avgScore)
    {
        char grade;

        if (avgScore >= 90)
        {
            grade = 'A';
        }
        else if (avgScore >= 80)
        {
            grade = 'B';
        }
        else if (avgScore >= 70)
        {
            grade = 'C';
        }
        else if (avgScore >= 60)
        {
            grade = 'D';
        }
        else
        {
            grade = 'F';
        }

        System.out.println("With that average, your grade is: " + grade);
    }
}

Answer 5

Try to change the main method to this:

public static void main(String args[]) {
    double avgScore = calculateAvg();
    printLetter(avgScore);
}