This code keeps giving me the error:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at fscgradebook.FSCgradebook.addRecord(FSCgradebook.java:54) at fscgradebook.FSCgradebook.main(FSCgradebook.java:145) /Users/john/Library/Caches/NetBeans/8.2/executor-snippets/run.xml:53: Java returned: 1 BUILD FAILED (total time: 0 seconds)

Why and how do i fix it?

Here is the code:

package fscgradebook;

import java.io.File; import java.io.PrintWriter; import java.util.Scanner;

/** * * @author john */ public class FSCgradebook {

// // METHODS USED TO PROCESS THE COMMANDS IN THE INPUT FILE. // - All we really do is print a small message for each command // // Method to Proccess ADDRECORD public static int addRecord(Scanner input, PrintWriter output, Student[] students) { int id = input.nextInt(); String fname = input.next(); String lname = input.next(); int g1 = input.nextInt(); int g2 = input.nextInt(); int g3 = input.nextInt(); int index = -1; Student s = new Student(fname, lname, id, g1, g2, g3, (((g2 * (0.3)) + (g3 * (0.4)) + (g1 * (0.3)))));

// save new student into array students[0] = s; output.println("Command: ADDRECORD"); output.println(fname + " " + lname + " (ID# " + id + ")" + " has been added to the FSC Grade Book"); output.println(" His final grade is " + (((g2 * (0.3)) + (g3 * (0.4)) + (g1 * (0.3)))) + "(" + ")"); for (int i = 0; i < Student.getNumStudents(); i++) { // < instead of <=, don't hardcode the length if (Student.getNumStudents() == 0) { students[0] = s; Student.increaseStudents(); return 0; // once we insert a, stop looping } for (int y =0; y < Student.getNumStudents(); y++) if (id < students[y].getID()){ index = y; } } if (index != 1){ for(int i = Student.getNumStudents()-1; i > index; i--){ students[i + 1] = students[i]; } students[index] = s; } else { students[Student.getNumStudents()] = s ; } Student.increaseStudents(); return index;

}

// Method to Proccess SEARCHBYID public static void searchbyID(PrintWriter output) { output.println("Command SEARCHBYID"); //if (Student.ID) == ) {

}

// Method to Proccess SEARCHBYNAME public static void searchbyNAME(PrintWriter output) { output.println("Command: SEARCHBYNAME"); }

// Method to Proccess DISPLAYSTATS public static void displaySTATS(PrintWriter output) { output.println("Command: DISPLAYSTATS"); //output.println("Statistical Results of"+course+"(Instructor: Dr "+instructor_fName+" "+instructor_lName+"):"); output.println(" Total number of student records: "); output.println(" Average Score: "); output.println(" Highest Score: "); output.println(" Lowest Score: "); output.println(" Total 'A' Grades: " + "(" + "% of class)"); output.println(" Total 'B' Grades: " + "(" + "% of class)"); output.println(" Total 'C' Grades: " + "(" + "% of class)"); output.println(" Total 'D' Grades: " + "(" + "% of class)"); output.println(" Total 'F' Grades: " + "(" + "% of class)"); }

// Method to Proccess DISPLAYSTUDENTS public static void displaySTUDENTS(PrintWriter output) { output.println("Command: DISPLAYSTUDENTS");

}

// Method to Proccess quit public static void QUIT(PrintWriter output) { output.println("Thank you for using the FSC Grade Book."); output.println("Goodbye."); }

//*************// // MAIN METHOD // //*************// public static void main(String[] args) throws Exception { // Variables needed for program String command; // used to save the command read from input file

//Student x = new Student(); //x.setFname("yh7yh6t"); //System.out.println(x.getFname()); // OPEN FILES // Input File: File inputFile = new File("FSCgradebook.in"); if (!inputFile.exists()) { System.out.println("Input file, " + inputFile + ", does not exist."); System.exit(0); } // Output File: File outputFile = new File("FSCgradebook.out");

// Make Scanner variable to read from input file, and // make Printwriter variable to print to output Scanner input = new Scanner(inputFile); PrintWriter output = new PrintWriter(outputFile);

String course = input.nextLine(); String instructor_fName = input.next(); String instructor_lName = input.next(); int maxNumberStudents = input.nextInt();

Student[] students = new Student[maxNumberStudents];

output.println("Welcome to the FSC Grade Book."); do { command = input.next();

// ADDRECORD if (command.equals("ADDRECORD") == true) { addRecord(input, output, students); } // *NOTE: // Notice, that we send the "output" variable (the PrintWriter variable) to the // method. This allows us to print to the file from inside the method. // You can also send the "input" variable to the method, which would allow you to // read from the file from inside the method also. // COMMAND2 else if (command.equals("SEARCHBYID") == true) { searchbyID(output); } // COMMAND3 else if (command.equals("SEARCHBYNAME") == true) { searchbyNAME(output); } else if (command.equals("DISPLAYSTATS") == true) { displaySTATS(output); } else if (command.equals("DISPLAYSTUDENTS") == true) { displaySTUDENTS(output); } // Command QUIT: Quit the Program else if (command.equals("QUIT") == true) { output.println("Thank you for using the FSC Grade Book."); output.println("Goodbye."); } // Invalid Command else { System.out.println("Invalid Command: input invalid."); }

} while (command.equals("QUIT") != true);

// Close input and output input.close(); output.close(); } }

Here is the student class:

package fscgradebook;

/** * * @author john */ public class Student {

private String fname; private String lname; int ID; private int[] examGrades; private double finalGrade; private char letterGrade; private static int numStudents = 0; private int maxNumStudents;

public Student() { } Student[] students = new Student[maxNumStudents];

public Student(String fname, String lname, int ID, int g1, int g2, int g3, double finalGrade) { this.fname = fname; this.lname = lname; this.ID = ID; this.finalGrade = finalGrade; examGrades = new int[3]; examGrades[0] = g1; examGrades[1] = g2; examGrades[2] = g3; }

public String getFname() { return fname; }

public void setFname(String fname) { this.fname = fname; }

public String getLname() { return lname; }

public void setLname(String lname) { this.lname = lname; }

public int getID() { return ID; }

public void setID(int ID) { this.ID = ID; }

public double getFinalGrade() { return finalGrade; }

public void setFinalGrade(double finalGrade) { this.finalGrade = finalGrade; }

public char getLetterGrade() { return letterGrade; }

public void setLetterGrade(char letterGrade) { this.letterGrade = letterGrade; }

public static int getNumStudents() { return numStudents; }

public static void setNumStudents(int numStudents) { Student.numStudents = numStudents; }

public static void increaseStudents(){ numStudents++; } }