I'm lost, need help figuring what todo?

[mike statham]

Been Fix thanks to you all!

Reposed the old code, after I learn I shouldn, sry agian

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class Dowhileloop
{
	public static void main(String[] args) throws FileNotFoundException
       
	{
   
     
   							
		String fileName = "grades.txt";
		File myFile = new File(fileName);
		

		try {
			Scanner input = new Scanner(myFile);
			String s = input.next();
         
         
      double grade = 0;
		int num = 0;
		int i=0;
		double sum = 0.0, ave = 0.0;
		
      while(i<num){

         
			
		sum += grade; 
         
     	i++;}
         
		 ave = sum / num;
            
        
		
		if(ave>=90)
		{
			System.out.print("You recieve an A\n");
		}
		else if(ave>=80)
		{
			System.out.print("You recieve a B\n");
		}
		else if(ave>=70)
		{
			System.out.print("You recieve a C\n");
		}
		else if(ave>=60)
		{
			System.out.print("You recieve a D\n");
		}
		else
		{
			System.out.print("You recieve a F\n");
		}
      
      } catch (FileNotFoundException ex)  {
		  System.out.println("Houston we have a problem: " + ex);
		  System.exit(1);
		}		

	}
}


 

[Manoj Kumar Jain]

what is the "key" ??

[Marco Galea]

you haven't declared "key" anywhere in your code that's why it's throwing that error. If you want to read the nextDouble you should use the reference you created for the Scanner object i.e. "scan"

grade = scan.nextDouble();

also i don't actually get the use of the do-while in the first place. i think you could have done for example

while (!scan.hasNextDouble()) 

but you'll still will have a problem cause you need to advance the scanner to the next new line and calculate the average for each "person" and print

[Greg Brannon]

You may want to scan each whole line from the file as a single String object, split() the line into an array of String objects at the " " (space), then parse the resulting String objects into the desired forms ( String, Double, Double, Double ). Repeat while lines exist in the file.

This approach works well if you're then creating objects from the data, say a Student object, in which to store the results.

[Winston Gutkowski]

Greg Brannon wrote:You may want to scan each whole line from the file as a single String object, split() the line into an array of String objects at the " " (space), then parse the resulting String objects into the desired forms ( String, Double, Double, Double ).

Totally agree. I dislike Scanner intensely.

Winston

[Stephan van Hulst]

Sorry for hijacking, but how come? I think Scanner is a wonderful class.

[Jeff Verdegan]

Stephan van Hulst wrote:Sorry for hijacking, but how come? I think Scanner is a wonderful class.

I've just never liked the color scheme.