Thread: GPA and average program

I know what I have wrong but I don't know how to fix it. The incorrect part is when using grades and average, because at the end, I get average=o. to due to having declared grades=0 but I don't know how to declare it outside and then inside the loop.
Right now it compiles without syntax errors but I cannot calculate the average correctly because the grades are not declare correctly.

First, your loop for (int count1 = 1; count1 <=6; count1++) does not execute 6 times, why? because of this statement:
count1=Integer.parseInt(trash); so when you input a number greater than 6 in Test1 it will terminate the loop since count1 is greater than 6 after the input.

You are confused why you always get an average of zero?
look at this statement in your code:
average=grades/numOfSubjects; //calculate average
your grades variable has a initial value of zero right? and you never write any value on it. so when your program reads that statement, it will be: average = 0 / numOfSubjects; and zero divided by any number would result to zero that is why you always got an average of zero.

I think this statement in your code :
count1=Integer.parseInt(trash);
should be like this:
grades=Integer.parseInt(trash); just a guess.

haha yeah you are right I didn't see that. I changed that but how I make sure that it stops when telling it to add less of 6 grades. Like if the student says 3 and once he adds the third grade, the program calculate the average directly instead of keep asking the rest of the tests' grades.

Also when calculating the average even when saying 100 to the 6 tests and get at the end 33.3333...etc.

--- Update ---

Actually it is dividing just one grade or the first one from the number of subjects idk how to declare the sum of unknown number of grades

Post your updated code, a sample run (copied from the output), and describe what's wrong with the sample run, giving what it should be.

I fixed some parts of my code but now it gives me an error at end saying:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4
at StudentReport.main(StudentReport.java:52)

This my new code:

/**
 * This program shows a database of students in a school.
 * It gathers information as name, classes, grades, and calculates average and gpa average.
 * 
 * @author Gerock7
 *
 */
import javax.swing.JOptionPane;
 
public class StudentReport 
{
	public static  void main(String[]args)
	{
		String name;
		String schoolName;
		String schoolGrade;
		int numOfSubjects;
		double grades;
		double average;
		String trash;
 
 
		name=JOptionPane.showInputDialog("Name:");           
		schoolGrade=JOptionPane.showInputDialog("Grade:");	  
		schoolName=JOptionPane.showInputDialog("School:");	  
 
 
 
		trash=JOptionPane.showInputDialog("Number of classes:");              
		numOfSubjects=Integer.parseInt(trash);				              			                                                                  
 
		trash=JOptionPane.showInputDialog("Test 1: ");
		grades=Double.parseDouble(trash);
 
		average=grades/numOfSubjects;
 
 
        double [] numbers = new double [ numOfSubjects];
 
		double sum=0;
 
 
		//get the grades added together in order to calculate the average
		for (int i = 2; i <=numOfSubjects; i++) 
				{
 
			trash=JOptionPane.showInputDialog("Test " + i + " : " );
			grades=Integer.parseInt(trash);
 
					sum += numbers [i];
 
				}
 
		average=sum/numOfSubjects;
 
 
		JOptionPane.showMessageDialog(null, "School name: " + schoolName + "\n"			
						+ "Student: "+ name + " \n "                                   
				                + "School grade: " + schoolGrade + "\n"	                                        
						+ "Average: " + average + ".");	                         	   
 
 
	}
 
}

okay, this.
ask first of how many grades would the student will enter.
input dialog must be : Enter no. of grades. - and store it in integer variable
then create a loop whose condition must be less than the no. of grades
for(int i = 1; i <= no. of grades; i++) or for(int i = 0; i < no. of grades; i++)
inside that loop get all the grades and add it in variable, lets say total variable whose initial value is zero.
something like total += grade something like that.
so after the loop you have now the total grades the student inputted.
then after the loop divide the total grades by no. of grade.
so lets say the student's no. of grade is 3. then he provided the grades 85, 86 and 87.
inside your loop your have now 85 + 86 + 87 = 258.
outside the loop divide it by the no. of grades so:
average = total / no. of grades
average = 258 / 3
average = 86.
got it? hope it helps. that is just a simple idea, but you can do it in different or better way.

Please don't post multiple threads on the same topic.

Threads merged.

thanks guys I made the proper changes and it is now working, I will still add some other things.
Again thanks