arrays and for loop java program coding

[itmajor1990]

Hello,

I'm in a beginning class for java programming and I can't seem to understand how to use the array and for loop together. I keep getting this message when I compile my program

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5
at GradeList.main(GradeList.java:43)


Here is my coding thus far

public class GradeList
{ 
        public static void main(String[] args)
        { // main method
	  // tell the user this program calculates grades for a class
	  System.out.println("This program calculates grades for a class of students");
          // declare variables
          int numStudents; 
	  int totalpts; 
	  int studentpts;
	  int k;
	  double percent;
	  char grade;
	  // input scanner
	  Scanner input = new Scanner(System.in);

	  // ask and get users input number of students and total possible points
	  System.out.print("Please Enter the Number of students: ");
	  numStudents = input.nextInt();
	  System.out.print("Please enter the Total Possible Points: ");
	  totalpts = input.nextInt();

	  // tell user to enter each students points
	  System.out.println("Please Enter Each Students Points");
	  System.out.println(" ");

	  // declare array
	  int [] studentList = new int [numStudents];

	  // input for loop
	  for (k=0; k <= numStudents; k++)
	  {
		  System.out.print("Points for Student " +k+1+ " ");
		  studentpts = input.nextInt();

	  while (studentpts > totalpts)
	  { // loop if user enters points greater than total 

		  // tell user invalid student points
		  System.out.println("Sorry that is over the total possible, try again");

		  // ask user again for student points
		  System.out.print("Points for student " +k+ " ");
		  studentpts = input.nextInt();
	  }
	  	  studentList[k] = studentpts;

	  }

	  // print formatted output for headings
	  String formathd= "CLASS OF " +numStudents+ " STUDENTS              POINTS     PERCENT     GRADE  ";

	  // format lines
	  String formatlns= "                                 ------     -------     -----  ";

	  // show variables and lines
	  System.out.println(formathd);
	  System.out.println(formatlns);

          // calculate percent and grade for each student points and store into percent array
	  for (k=0; k < numStudents; k++)
	  {
		  percent = studentList[k] *100;
	  if (percent >= 90.00 
	  	{
	  grade = 'A';
	  	}
	  else if (percent >= 80.00)
	  	{
          grade = 'B';
	  	}
	  else if (percent >= 70.00)
	  	{
          grade = 'C';
	  	}
	  else if (percent >= 60.00)
          	{
          grade = 'D';
	  	}
	  else
  	  	{
		grade= 'F';
		}
	  String format= "%25s      %11d     %11.2f     %9c";
	  System.out.printf(format, studentList[k], percent, grade);
	  }

  
        } // end of main method
} // end of class

[pbrockway2]

// declare array
int [] studentList = new int [numStudents];
 
// input for loop
for (k=0; k <= numStudents; k++;)
{

    // ...

    studentList[k] = studentpts;
}

This doesn't look right to me. The for loop goes to high: when k equals numStudents then studentlist[k] will be out of bounds.

[itmajor1990]

I changed it to

	  // input array
	  int [] studentList = new int [numStudents];

	  // input for loop
	  for (k=0; k < numStudents; k++)
	  {
		  System.out.print("Points for Student " +k+1+ " ");
		  studentList[k] = input.nextInt();

	  while (studentList[k] > totalpts)
	  { // loop if user enters points greater than total 

		  // tell user invalid student points
		  System.out.println("Sorry that is over the total possible, try again");

		  // ask user again for student points
		  System.out.print("Points for student " +k+ " ");
		  studentList[k] = input.nextInt();
	  }
	  }

It still gives me same error.

[pbrockway2]

Could you confirm that the exception occurs on the "studentList[k] = input.nextInt();" line (or lines)?

Try printing the values of k and numStudents just before the exception occurs to check that they have the values you think they should have.

[itmajor1990]

This is how it prints once I compile and run my coding:

java GradeList
This program calculates grades for a class of students
Please Enter the Number of students: 5
Please enter the Total Possible Points: 380
Please Enter Each Students Points

Points for Student 1 327
Points for Student 2 397
Sorry that is over the total possible, try again
Points for student 2 297
Points for Student 3 356
Points for Student 4 246
Points for Student 5 295
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5
at GradeList.main(GradeList.java:43)

[pbrockway2]

That output doesn't seem to come from that code. (In the code one prompt uses k+1 the other uses k). Also the exception line number is the same - which may just be a coincidence, but it's suspicious. Perhaps you're running old code.

Also, do check (with System.out.println()) the values of k and numStudents just before the exception occurs.