While Loop Not Reading First Integer

[Collin Sampson]

This is my code, I am new to java so bear with me. I have to make a program that reads in exam scores and outputs, number of A's, B's...etc. and percentages relatively. I am using a while loop but it is not reading the first score. I input 90 90 90 90 90 60 60 60 60 60 -1(sentinel value) and it outputs that there are 4 A's, and 5 D's. Help!

import java.util.*;

public class GradeProgram
{

    public static void main(String[] args)
    {
    	
    System.out.println("Put in atleast ten exam scores as integer");
    System.out.println("percentages, ranging from 0 to 100. Put in a");
    System.out.println("negative number as the end marker.");
    
    Scanner keyboard = new Scanner(System.in);
    
    int next, count = 0;
    int numberOfAs = 0, numberOfBs = 0, numberOfCs = 0;
    int numberOfDs = 0, numberOfFs = 0;
    double percentAs, percentBs, percentCs;
    double percentDs, percentFs;
    
    next = keyboard.nextInt( );
    while(next >= 0)
    {
    	count++;
    	next = keyboard.nextInt( );
    	
    if ((next < 60) && (next >= 0))
    	numberOfFs++;
    else if ((next >= 60) && (next < 70))
    	numberOfDs++;
    else if ((next >= 70) && (next < 80))
    	numberOfCs++;
    else if ((next >= 80) && (next < 90))
    	numberOfBs++;
    else if ((next >= 90) && (next <= 100))
    	numberOfAs++;
    
    }
    
    if (count == 0)
    	System.out.println("No scores entered.");
    else
    {
  	System.out.println("Number of scores: " + count);
    	percentAs = numberOfAs / (double)count;
    	System.out.println("Number of A's: " + numberOfAs + " which is " 
    		+ percentAs + " %");
    	percentBs = numberOfBs / (double)count;
    	System.out.println("Number of B's: " + numberOfBs + " which is " 
    		+ percentBs + " %");
    	percentCs = numberOfCs / (double)count;
    	System.out.println("Number of C's: " + numberOfCs + " which is " 
    		+ percentCs + " %");
    	percentDs = numberOfDs / (double)count;
    	System.out.println("Number of D's: " + numberOfDs + " which is " 
    		+ percentDs + " %");
    	percentFs = numberOfFs / (double)count;
    	System.out.println("Number of F's: " + numberOfFs + " which is " 
    		+ percentFs + " %");
  	}
  	
    }
    
}

[gimmy kaye]

I miss what this question has to do with servlets.

I think there's something wrong with the logic of yor program.

try this loop:

next = keyboard.nextInt( );

while(next >= 0) 
{ 

if ((next < 60) && (next >= 0)) 
numberOfFs++; 
else if ((next >= 60) && (next < 70)) 
numberOfDs++; 
else if ((next >= 70) && (next < 80)) 
numberOfCs++; 
else if ((next >= 80) && (next < 90)) 
numberOfBs++; 
else if ((next >= 90) && (next <= 100)) 
numberOfAs++; 

count++; 
next = keyboard.nextInt( ); 

} 

[Tim Hagberg]

The first time you call nextInt() (right before your while loop), you're reading your first number in. Then before you do anything with that value, within the body of the while loop you are calling nextInt() again.

[Winston Gutkowski]

Chaps, please UseCodeTags.

Thanks.

Winston

[Campbell Ritchie]

System.out.print("Enter first number, negative to skip loop entirely: ");
while ((mark = inScan.nextInt()) >= 0)
{
   if (...)
   ...
   else if ...
   ...
   else
   ...
   System.out.print("Enter next number, negative to finish: "); // Last line of loop
}

That is an idiom you would never guess, ensuring you read the number once per loop.

[Winston Gutkowski]

Collin Sampson wrote:I am using a while loop but it is not reading the first score. I input 90 90 90 90 90 60 60 60 60 60 -1(sentinel value) and it outputs that there are 4 A's, and 5 D's. Help!

I think gimmy covered it, but there is a way of doing that doesn't involve repetition, viz:

int next;
while(next = keyboard.nextInt()) >= 0)
{
   if (next > 100) {
      System.out.println("invalid input: " + next);
      continue;
   }
   if (next >= 90)
    	numberOfAs++;
   else if (next >= 80)
    	numberOfBs++;
   else if (next >= 70)
    	numberOfCs++;
   else if (next >= 60)
    	numberOfDs++;
   else
    	numberOfFs++;
   count++;
}

and, as you can see, you don't have to check for a range every time.

I did wonder what happened to the 'E's though.

Winston

[Edit] Too slow

[Campbell Ritchie]

I added code tags to one post and you can see how much better it looks, but the other wasn’t indented.

[Collin Sampson]

Thank you all for your help, I really appreciate it. I see where I went wrong. Sorry im such a noob =D. This is my first loop program and we haven't really covered it yet in class.

[Campbell Ritchie]

This is slightly changed from what Winston Gutkowski wrote:

int next;
while(next = keyboard.nextInt()) >= 0)
{
   if (next > 100) {
      System.out.println("invalid input: " + next);
//    continue;
   }
   else if (next >= 90)
    	numberOfAs++;
   else if (next >= 80)
    	numberOfBs++;
   else if (next >= 70)
    	numberOfCs++;
   else if (next >= 60)
    	numberOfDs++;
   else
    	numberOfFs++;
   count++;
}

. . .

Winston

I have changed that slightly, replacing the continue with an else, so as to maintain structured programming. There, everybody can disagree with me about structured programming

Winston Gutkowski wrote:[Edit] Too slow

I’ve been taking lessons from Rob!

[Winston Gutkowski]

Campbell Ritchie wrote:I have changed that slightly, replacing the continue with an else, so as to maintain structured programming. There, everybody can disagree with me about structured programming

Hey, I grew up with Dijkstra

Removing the continue means that count will include invalid entries, which I assumed was not Collin's intention.

Winston

[Campbell Ritchie]

I missed the count++. Sorry. You would have to put the count++ in {} after the first else. Then it would ignore marks of 101%.