Thread: String array problem

This is what my program looks like

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Scanner;
 
 
public class mypa9class {
 
	/**
	 * @param args
	 * @throws IOException 
	 */
	public static void main(String[] args) throws IOException {
 
		// get all files and input in arrays
 
		// name array
		int max = 9;
		File last = new File("Lname.txt");
		Scanner sclast = new Scanner(last);
		File first = new File("Fname.txt");
		Scanner scfirst = new Scanner(first);
		String[] namearray = new String[max];
		String firstname;
		String lastname;
 
		for (int i = 0; i < 10; i++)
		{
		firstname = scfirst.next();
		lastname = sclast.next();
		namearray[i] = firstname + " " + lastname;
		}
 
		// exam 1
		double average1 = 0;
		double max1 = 0;
		double min1 = 0;
		File exam1 = new File("Exam1.txt");
		Scanner scexam1 = new Scanner(exam1);
		double[] exarray1 = new double[max];
		int count = 0;
		while (scexam1.hasNext())
				{
			exarray1[count] = scexam1.nextDouble();
			count++;
				}
		average1 = getAvg(exarray1);		
//		System.out.println("average1 " + average1);
 
		max1 = getMax(exarray1);
//		System.out.println("max1 " + max1);
 
		min1 = getMin(exarray1);
//		System.out.println("min1 " + min1);
 
		// exam 2
		double average2 = 0;
		double max2 = 0;
		double min2 = 0;
		File exam2 = new File("Exam2.txt");
		Scanner scexam2 = new Scanner(exam2);
		double[] exarray2 = new double[max];
		count = 0;
		while (scexam2.hasNext())
				{
			exarray2[count] = scexam2.nextDouble();
			count++;
				}
		average2 = getAvg(exarray2);
//		System.out.println("average2 " +average2);
		max2 = getMax(exarray2);
//		System.out.println("max2 " + max2);
		min2 = getMin(exarray2);
//		System.out.println("min2 " + min2);
 
		// exam 3
		double average3 = 0;
		double max3 = 0;
		double min3 = 0;
		File exam3 = new File("Exam3.txt");
		Scanner scexam3 = new Scanner(exam3);
		double[] exarray3 = new double[max];
		count = 0;
		while (scexam3.hasNext())
				{
			exarray3[count] = scexam3.nextDouble();
			count++;
				}
		average3 = getAvg(exarray3);
//		System.out.println("average3 " + average3);
		max3 = getMax(exarray3);
//		System.out.println("max3 " +max3);
		min3 = getMin(exarray3);
//		System.out.println("min3 " + min3);
 
		// exam 4
		double average4 = 0;
		double max4 = 0;
		double min4 = 0;
		File exam4 = new File("Exam4.txt");
		Scanner scexam4 = new Scanner(exam4);
		double[] exarray4 = new double[max];
		count = 0;
		while (scexam4.hasNext())
				{
			exarray4[count] = scexam4.nextDouble();
			count++;
				}
		average4 = getAvg(exarray4);
//		System.out.println("average4 " + average4);
		max4 = getMax(exarray4);
//		System.out.println("max4 " + max4);
		min4 = getMin(exarray4);
//		System.out.println("min4 " + min4);
 
 
//	System.out.println(namearray[9]);
//	System.out.println(exarray4[9]);
 
	// calculate average for students and input in a new array called exAvg
	double[] exAvg = new double[max];
	for (int i = 0; i < 10; i++)
	{
	exAvg[i] = computeAverage(exarray1[i], exarray2[i], exarray3[i], exarray4[i])	;
 
	}
 
	// calculate grade for each student and input it in a new array titled grade
	char[] grade = new char[max];
	for (int i = 0; i < 10; i++)
	{
		grade[i] = computeGrade(exAvg[i]);
	}
 
 
	//output area + printwriter
	PrintWriter prw = new PrintWriter("PAOutFile.txt");
 
	System.out.println("Full Name of Student \t\t Ex1 \t Ex2 \t Ex3 \t Ex4 \t Avg \t Grade");
	prw.println("Full Name of Student \t\t Ex1 \t Ex2 \t Ex3 \t Ex4 \t Avg \t Grade");
	for (int i = 0; i < 10; i++)
	{
		System.out.println(namearray[i] + "\t\t\t" + exarray1[i] + "\t" + exarray2[i] + "\t" + exarray3[i] + "\t" + exarray4[i] + "\t" + exAvg[i] + "\t" + grade[i]);
		prw.println(namearray[i] + "\t\t\t\t\t" + exarray1[i] + "\t" + exarray2[i] + "\t" + exarray3[i] + "\t" + exarray4[i] + "\t" + exAvg[i] + "\t" + grade[i]);
	}
	System.out.println();
	System.out.println("Exam Number \t\t\t Max Score \t Min Score \t Average Score");
	System.out.println("Exam 1 \t\t\t\t " + max1 + "\t\t" + min1 + "\t\t\t" + average1);
	System.out.println("Exam 2 \t\t\t\t " + max2 + "\t\t" + min2 + "\t\t\t" + average2);
	System.out.println("Exam 3 \t\t\t\t " + max3 + "\t\t" + min3 + "\t\t\t" + average3);
	System.out.println("Exam 4 \t\t\t\t " + max4 + "\t\t" + min4 + "\t\t\t" + average4);
	prw.println("Exam Number \t\t\t Max Score \t Min Score \t Average Score");
	prw.println("Exam 1 \t\t\t\t " + max1 + "\t\t" + min1 + "\t\t\t" + average1);
	prw.println("Exam 2 \t\t\t\t " + max2 + "\t\t" + min2 + "\t\t\t" + average2);
	prw.println("Exam 3 \t\t\t\t " + max3 + "\t\t" + min3 + "\t\t\t" + average3);
	prw.println("Exam 4 \t\t\t\t " + max4 + "\t\t" + min4 + "\t\t\t" + average4);
 
	prw.close();
	}
	public static double getAvg(double[] exam)
	{
		double average = 0;
		double total = 0;
		//average exam
		for (int i = 0; i < 10; i++)
		{
			total = total + exam[i];
 
		}
		average = total/10;
 
		return(average);
	}
 
	public static double getMax(double[] exam)
	{
		double max = 0;
		for (int i = 0; i < 10; i++)
		{
			if (max < exam[i])
			{
				max = exam[i];
			}
		}
 
 
		return(max);
	}
 
	public static double getMin(double[] exam)
	{
		double min = 999;
		for (int i = 0; i <10; i ++)
		{
			if (min > exam[i])
			{
				min = exam[i];
			}
		}
 
		return(min);
 
	}
 
	public static double computeAverage(double exam1, double exam2, double exam3, double exam4)
	{
		double studavg = 0;
		studavg = (exam1 + exam2 + exam3 + exam4) / 4;
 
		return(studavg);
	}
 
	public static char computeGrade(double avgrade)
	{
		char grade = 'E';
		if (avgrade >= 90)
		{
			grade = 'A';
		}
		if (avgrade < 90 && avgrade >= 80)
		{
			grade = 'B';
		}
		if (avgrade < 80 && avgrade >= 70)
		{
			grade = 'C';
		}
		if (avgrade < 70 && avgrade >= 60)
		{
			grade = 'D';
		}
		if (avgrade <60)
		{
			grade = 'E';
		}
 
		return (grade);
	}
	}

Error Code

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 9
	at mypa9class.main(mypa9class.java:32)

There is much more code, but i am just wondering why this gives me an error, when i switch the length of the array to 10 instead of 9 i have no problems. The scanners bring in names from two different text files both with have 10 names each. When making the array i figured 0,1,2, -> 9 would give me the 10 spots i need i don't understand why i need it a 10 which would in turn leave namearry[10] to have nothing in it?
Let me know if i didn't explain my question good enough.

I edited to add my full code, i know where the error occurs its because i changed max = 9 instead of 10, i just can't figure out logically why a 9 will not work. In my for loop its actually <10 which means it will run 10 times including 0 so i don't know why i need an array of [10] which is 11 locations.

Originally Posted by hwhelp

.... an array of [10] which is 11 locations.

myArray[10] gives:
myArray[0], myArray[1], myArray[2], myArray[3], myArray[4], myArray[5], myArray[6], myArray[7], myArray[8], myArray[9]
which comes to 10 elements, not 11

Also note that I had errors in my previous post which may have been misleading, and the errors have been corrected.

--- Update ---

Originally Posted by hwhelp

.... an array of [10] which is 11 locations.

myArray[10] gives:
myArray[0], myArray[1], myArray[2], myArray[3], myArray[4], myArray[5], myArray[6], myArray[7], myArray[8], myArray[9]
which comes to 10 elements, not 11

Also note that I had errors in my previous post which may have been misleading, and the errors have been corrected.

Thats where i was confused, thank you so much !!