Develop Reference

Can't loop properly through list of objects

I'm having the following issue.
I have a list filled with instances of the "God" class, 12 instances, for now, but will add more in the future.
I also have an list empty.
Both lists can take type God instances.
The user will pick 6 of these gods, and these gods will be added to the empty list, and also be remove of the filled list, so they can't get picked again.
The goal of this part of the project is, to:
The user will pick 6 times. So I have a for loop from 0 to 5;
The Scanner takes the id of the god
The second for loop, from 0 to listFilledWithGods.size(), will check if the scanner matches the id
If the id matches, it will add to the empty list, and remove from the List filled with gods
If it does not match the user needs to be asked constantly to pick another one, until the user picks an available god. (here is where I'm having trouble)
Github: https://github.com/OrlandoVSilva/battleSimulatorJava.git
The issue in question resides in the class player in the method selectGodsForTeam
There is a JSON jar added to the project: json-simple-1.1.1
*Edit:
I added the while loop, as an exmaple of one of the ways that I tried to fix the issue.
If the user on the first pick picks id 3, it should work, because no god has been picked yet, however the loop when comparing it with the first position (id 1) it says to pick another one, which should is not the intended objective.
Main:
import java.util.List;
public class Main {
public Main() {
}
public static void main(String[] args) {
Launcher launch = new Launcher();
godSelection(launch.loadGods());
}
private static void godSelection(List<God> listOfloadedGods) {
Player player = new Player(listOfloadedGods);
player.selectGodsForTeam();
}
}
Launcher:
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.List;
public class Launcher {
private List<God> godCollection;
public Launcher(){
godCollection = new ArrayList<>();
}
List<God> loadGods(){ // load all gods from Json file into list
String strJson = getJSONFromFile("C:\\Users\\OrlandoVSilva\\Desktop\\JavaBattleSimulator\\battlesimulator\\src\\projectStructure\\gods.json");
// Try-catch block
try {
JSONParser parser = new JSONParser();
Object object = parser.parse(strJson); // converting the contents of the file into an object
JSONObject mainJsonObject = (JSONObject) object; // converting the object into a json object
//-------------------
JSONArray jsonArrayGods = (JSONArray) mainJsonObject.get("gods");
//System.out.println("Gods: ");
for(int i = 0; i < jsonArrayGods.size(); i++){
JSONObject jsonGodsData = (JSONObject) jsonArrayGods.get(i);
String godName = (String) jsonGodsData.get("name");
//System.out.println("Name: " + godName);
double godHealth = (double) jsonGodsData.get("health");
//System.out.println("Health: " + godHealth);
double godAttack = (double) jsonGodsData.get("attack");
//System.out.println("Attack: " + godAttack);
double godSpecialAttack = (double) jsonGodsData.get("specialAttack");
//System.out.println("Special Attack: " + godSpecialAttack);
double godDefense = (double) jsonGodsData.get("defense");
//System.out.println("Defense: " + godDefense);
double godSpecialDefence = (double) jsonGodsData.get("specialDefense");
//System.out.println("Special Defence: " + godSpecialDefence);
double godSpeed = (double) jsonGodsData.get("speed");
//System.out.println("Speed: " + godSpeed);
double godMana = (double) jsonGodsData.get("mana");
//System.out.println("Mana: " + godMana);
String godPantheon = (String) jsonGodsData.get("pantheon");
//System.out.println("Pantheon: " + godPantheon);
long godId = (long) jsonGodsData.get("id");
int newGodId = (int) godId;
//System.out.println("Id: " + newGodId);
godCollection.add(new God(godName, godHealth, godAttack, godSpecialAttack, godDefense, godSpecialDefence, godSpeed, godMana, godPantheon, newGodId));
//System.out.println();
}
} catch (Exception ex){
ex.printStackTrace();
}
// Try-catch block
//System.out.println("Size: " + godCollection.size());
return godCollection;
}
public static String getJSONFromFile(String filename) { // requires file name
String jsonText = "";
try {
BufferedReader bufferedReader = new BufferedReader(new FileReader(filename)); // read the file
String line; // read the file line by line
while ((line = bufferedReader.readLine()) != null) {
jsonText += line + "\n"; // store json dat into "jsonText" variable
}
bufferedReader.close();
} catch (Exception e) {
e.printStackTrace();
}
return jsonText;
}
}
Player:
import java.util.*;
public class Player {
// --- Properties ---
private List<God> listOfAllGods; // List of all the gods;
private List<God> selectedGods; // list for the selected gods;
// --- Properties ---
// --- Constructor ---
Player(List<God> listOfAllGods){
this.listOfAllGods = listOfAllGods;
selectedGods = new ArrayList<>();
}
// --- Constructor ---
// --- Getters & Setters ---
public List<God> getSelectedGods() {
return listOfAllGods;
}
// --- Getters & Setters ---
// --- Methods ---
void selectGodsForTeam(){
Scanner scanner = new Scanner(System.in);
boolean isGodAvailable;
int chooseGodId;
/*
char answerChar = 'n';
while (answerChar == 'n'){
answerChar = informationAboutGods();
// Do you want to see information about any of the gods first?
// y or n
while(answerChar == 'y'){
answerChar = informationAboutAnyOtherGods();
// Which of the gods, do you want to see information of?
// godId
// Do you want to see information about any other gods?
// y or n
}
answerChar = proceedWithGodPick();
// Do you want to proceed with the God pick?
// y or n
}
System.out.println();
*/
System.out.println("Please choose the 6 id's of the gods, you wish to pick:");
for(int i = 0; i <= 5; i++){
chooseGodId = scanner.nextInt();
for(int j = 0; j < listOfAllGods.size(); j++){
if(chooseGodId == listOfAllGods.get(j).getId()){
selectedGods.add(listOfAllGods.get(j));
listOfAllGods.remove(j);
} else {
isGodAvailable = false;
while (!isGodAvailable){
System.out.println("Please pick another one");
chooseGodId = scanner.nextInt();
if(chooseGodId == listOfAllGods.get(j).getId()) {
isGodAvailable = true;
selectedGods.add(listOfAllGods.get(j));
listOfAllGods.remove(j);
}
}
}
}
}
}
char informationAboutGods(){
Scanner scanner = new Scanner(System.in);
char answerChar = 'n';
//-----------
System.out.println("This is a list, of all the selectable gods: ");
System.out.println();
for (int i = 0; i < listOfAllGods.size(); i++){
System.out.println(listOfAllGods.get(i).getName() + " = " + "Id: " + listOfAllGods.get(i).getId());
}
System.out.println();
System.out.println("Do you want to see information about any of the gods first?");
System.out.println("[y] or [n]");
answerChar = scanner.next().charAt(0);
return answerChar;
}
char informationAboutAnyOtherGods(){
Scanner scanner = new Scanner(System.in);
char answerChar = 'n';
int answerInt;
//------------
System.out.println();
System.out.println("Which of the gods, do you want to see information of?");
System.out.println("Please input it's id number: ");
answerInt = scanner.nextInt();
System.out.println();
System.out.println("Display god information here!");
System.out.println();
System.out.println("Do you want to see information about any other gods?");
System.out.println("[y] or [n]");
answerChar = scanner.next().charAt(0);
return answerChar;
}
char proceedWithGodPick(){
Scanner scanner = new Scanner(System.in);
char answerChar = 'n';
//----------
System.out.println();
System.out.println("Do you want to proceed with the God pick?");
System.out.println("[y] or [n]");
answerChar = scanner.next().charAt(0);
return answerChar;
}
// --- Methods ---
}
God:
public class God {
private final String name;
private double health;
private double attack;
private double specialAttack;
private double defense;
private double specialDefense;
private double speed;
private double mana;
private final String pantheon;
private final int id;
public God(String name, double health, double attack, double specialAttack, double defense, double specialDefense, double speed, double mana, String pantheon, int id) {
this.name = name;
this.health = health;
this.attack = attack;
this.specialAttack = specialAttack;
this.defense = defense;
this.specialDefense = specialDefense;
this.speed = speed;
this.mana = mana;
this.pantheon = pantheon;
this.id = id;
}
public double getHealth() {
return this.health;
}
public void setHealth(double health) {
this.health = health;
}
public double getAttack() {
return this.attack;
}
public void setAttack(double attack) {
this.attack = attack;
}
public double getSpecialAttack() {
return this.specialAttack;
}
public void setSpecialAttack(double specialAttack) {
this.specialAttack = specialAttack;
}
public double getDefense() {
return this.defense;
}
public void setDefense(double defense) {
this.defense = defense;
}
public double getSpecialDefense() {
return this.specialDefense;
}
public void setSpecialDefense(double specialDefense) {
this.specialDefense = specialDefense;
}
public double getSpeed() {
return this.speed;
}
public void setSpeed(double speed) {
this.speed = speed;
}
public double getMana() {
return this.mana;
}
public void setMana(double mana) {
this.mana = mana;
}
public String getName() {
return this.name;
}
public String getPantheon() {
return this.pantheon;
}
public int getId() {
return this.id;
}
}

If I understand correctly, the key is to replace the for loop, which will have 6 iterations, with a while loop, which will iterate until the user has successfully selected 6 gods. Use continue; when there is a failure to select a god.
System.out.println("Please choose the 6 id's of the gods, you wish to pick:");
while (selectedGods.size () < 6) {
System.out.print ("You have selected " + selectedGods.size ()
+ "gods. Please enter I.D. of next god >");
chooseGodId = scanner.nextInt();
if (findGod (selectedGods, chooseGodID) >= 0) {
System.out.println ("You already selected god " + chooseGodId
+ ". Please select again.");
continue;
}
int godSelectedIndex = findGod (listOfAllGods, chooseGodId);
if (godSelectedIndex < 0) {
System.out.println ("God " + chooseGodID + " is not available."
+ " Please select again.");
continue;
}
selectedGods.add (listOfAllGods.get(godSelectedIndex));
listOfAllGods.remove (godSelectedIndex);
}
This assumes the existence of
static public int findGod (List<God> godList, int targetGodID)
This findGod method searches godList for an element in which .getId() is equal to gargetGodID. When a match is found, it returns the index of element where the match was found. When a match is not found, it returns -1. The O/P has shown the ability to create this method.
Note: I have not verified the code in this answer. If you find an error, you may correct it by editing this answer.

how do i collect everything after a certain substring value

in here i want to collect everything after a substring and set it as their specfic field.
import java.util.ArrayList;
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
/**
*
*
* class StudentReader for retrieveing data from file
*
*/
public class StudentReader {
public static Student[] readFromTextFile(String fileName) {
ArrayList<Student> result = new ArrayList<Student>();
File f = new File(filename);
Scanner n = new Scanner(f);
while (n.hasNextLine()) {
String text = n.nextLine();
}
n.close();
String hold1[] = text.Split(",");
String hold2[] = new String[hold1.length];;
for(int i = 0; i < hold1.length(); ++i) {
hold2[i] = hold1.Split("=");
if (hold2[i].substring(0,3).equals("name")) {
}
}
return result.toArray(new Student[0]);
}
}
backing up the goal of this code is to first open and read a file where it has about 20 lines that look just like this
Student{name=Jill Gall,age=21,gpa=2.98}
I then need to split it as done above, twice first to get rid of comma and the equals, I then for each line need to collect the value of the name, age and double, parse them and then set them as a new student object and return that array they are going to be saved onto, what I am currently stuck on is that i cannot figure out what's the right code here for collecting everything after "name" "age" "gpa", as i dont know how to set specific substrings for different name
im using this link as a reference but I don't see what actually does it
How to implement discretionary use of Scanner

I think the bug is in following lines,
while (n.hasNextLine()) {
String text = n.nextLine();
}
Above code should throw compilation error at String hold1[] = text.Split(","); as text is local variable within while loop.
Actual it should be,
List<String> inputs = new ArrayList<String>()
Scanner n = new Scanner(f);
while (n.hasNextLine()) {
inputs.add(n.nextLine());
}
You can use above inputs list to manipulate your logic

By the look of it, at least by your ArrayList<> declaration, you have a class named Student which contains member variable instances of studentName, studentAge, and studentGPA. It might look something like this (the Getter/Setter methods are of course optional as is the overriden toString() method):
public class Student {
// Member Variables...
String studentName;
int studentAge = 0;
double studentGPA = 0.0d;
// Constructor 1:
public Student() { }
// Constructor 2: (used to fill instance member variables
// right away when a new instance of Student is created)
public Student(String name, int age, double gpa) {
this.studentName = name;
this.studentAge = age;
this.studentGPA = gpa;
}
// Getters & Setters...
public String getStudentName() {
return studentName;
}
public void setStudentName(String studentName) {
this.studentName = studentName;
}
public int getStudentAge() {
return studentAge;
}
public void setStudentAge(int studentAge) {
this.studentAge = studentAge;
}
public double getStudentGPA() {
return studentGPA;
}
public void setStudentGPA(double studentGPA) {
this.studentGPA = studentGPA;
}
#Override
public String toString() {
return new StringBuilder("").append(studentName).append(", ")
.append(String.valueOf(studentAge)).append(", ")
.append(String.valueOf(studentGPA)).toString();
}
}
I should think the goal would be to to read in each file line from the Students text file where each file line consists of a specific student's name, the student's age, and the student's GPA score and create a Student instance for the Student on that particular file line. This is to be done until the end of file. If there are twenty students within the Students text file then, when the readFromTextFile() method has completed running there will be twenty specific instances of Student. Your StudentReader class might look something like this:
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
/**
*
* class StudentReader for retrieving data from file
*
*/
public class StudentReader {
private static final Scanner userInput = new Scanner(System.in);
private static Student[] studentsArray;
public static void main(String args[]) {
String underline = "=====================================================";
String dataFilePath = "StudentsFile.txt";
System.out.println("Reading in Student data from file named: " + dataFilePath);
if (args.length >= 1) {
dataFilePath = args[0].trim();
if (!new File(dataFilePath).exists()) {
System.err.println("Data File Not Found! (" + dataFilePath + ")");
return;
}
}
studentsArray = readFromTextFile(dataFilePath);
System.out.println("Displaying student data in Console Window:");
displayStudents();
System.out.println(underline);
System.out.println("Get all Student's GPA score average:");
double allGPA = getAllStudentsGPAAverage();
System.out.println("GPA score average for all Students is: --> " +
String.format("%.2f",allGPA));
System.out.println(underline);
System.out.println("Get a Student's GPA score:");
String sName = null;
while (sName == null) {
System.out.print("Enter a student's name: --> ");
sName = userInput.nextLine();
/* Validate that it is a name. Should validate in
almost any language including Hindi. From Stack-
Overflow post: https://stackoverflow.com/a/57037472/4725875 */
if (sName.matches("^[\\p{L}\\p{M}]+([\\p{L}\\p{Pd}\\p{Zs}'.]*"
+ "[\\p{L}\\p{M}])+$|^[\\p{L}\\p{M}]+$")) {
break;
}
else {
System.err.println("Invalid Name! Try again...");
System.out.println();
sName = null;
}
}
boolean haveName = isStudent(sName);
System.out.println("Do we have an instance of "+ sName +
" from data file? --> " +
(haveName ? "Yes" : "No"));
// Get Student's GPA
if (haveName) {
double sGPA = getStudentGPA(sName);
System.out.println(sName + "'s GPA score is: --> " + sGPA);
}
System.out.println(underline);
}
public static Student[] readFromTextFile(String fileName) {
List<Student> result = new ArrayList<>();
File f = new File(fileName);
try (Scanner input = new Scanner(f)) {
while (input.hasNextLine()) {
String fileLine = input.nextLine().trim();
if (fileLine.isEmpty()) {
continue;
}
String[] lineParts = fileLine.split("\\s{0,},\\s{0,}");
String studentName = "";
int studentAge = 0;
double studentGPA = 0.0d;
// Get Student Name (if it exists).
if (lineParts.length >= 1) {
studentName = lineParts[0].split("\\s{0,}\\=\\s{0,}")[1];
// Get Student Age (if it exists).
if (lineParts.length >= 2) {
String tmpStrg = lineParts[1].split("\\s{0,}\\=\\s{0,}")[1];
// Validate data.
if (tmpStrg.matches("\\d+")) {
studentAge = Integer.valueOf(tmpStrg);
}
// Get Student GPA (if it exists).
if (lineParts.length >= 3) {
tmpStrg = lineParts[2].split("\\s{0,}\\=\\s{0,}")[1];
// Validate data.
if (tmpStrg.matches("-?\\d+(\\.\\d+)?")) {
studentGPA = Double.valueOf(tmpStrg);
}
}
}
}
/* Create a new Student instance and pass the student's data
into the Student Constructor then add the Student instance
to the 'result' List. */
result.add(new Student(studentName, studentAge, studentGPA));
}
}
catch (FileNotFoundException ex) {
System.err.println(ex);
}
return result.toArray(new Student[result.size()]);
}
public static void displayStudents() {
if (studentsArray == null || studentsArray.length == 0) {
System.err.println("There are no Students within the supplied Students Array!");
return;
}
for (int i = 0; i < studentsArray.length; i++) {
System.out.println(studentsArray[i].toString());
}
}
public static boolean isStudent(String studentsName) {
boolean found = false;
if (studentsArray == null || studentsArray.length == 0) {
System.err.println("There are no Students within the supplied Students Array!");
return found;
} else if (studentsName == null || studentsName.isEmpty()) {
System.err.println("Student name can not be Null or Null-String (\"\")!");
return found;
}
for (int i = 0; i < studentsArray.length; i++) {
if (studentsArray[i].getStudentName().equalsIgnoreCase(studentsName)) {
found = true;
break;
}
}
return found;
}
public static double getStudentGPA(String studentsName) {
double score = 0.0d;
if (studentsArray == null || studentsArray.length == 0) {
System.err.println("There are no Students within the supplied Students Array!");
return score;
} else if (studentsName == null || studentsName.isEmpty()) {
System.err.println("Student name can not be Null or Null-String (\"\")!");
return score;
}
boolean found = false;
for (int i = 0; i < studentsArray.length; i++) {
if (studentsArray[i].getStudentName().equalsIgnoreCase(studentsName)) {
found = true;
score = studentsArray[i].getStudentGPA();
break;
}
}
if (!found) {
System.err.println("The Student named '" + studentsName + "' could not be found!");
}
return score;
}
public static double getAllStudentsGPAAverage() {
double total = 0.0d;
if (studentsArray == null || studentsArray.length == 0) {
System.err.println("There are no Students within the supplied Students Array!");
return total;
}
for (int i = 0; i < studentsArray.length; i++) {
total += studentsArray[i].getStudentGPA();
}
return total / (double) studentsArray.length;
}
}

How to add in a read object to an ArrayList and print out user requested info

For class, we have to read in a CSV file that has states, their abbreviations, and population and add the objects to an array list. then we have to print out the list in a tabular format. From there we have to ask the user what abbreviation they are looking for and print the abbreviation, state, and population out.
I have already tried adding the objects to an array list how my professor showed me and it broke the whole program. From what I have it set up as now is the closest thing that i've gotten to from the assignment description. We have never used array lists before so you'll have to forgive me if im missing something obvious. I have tried adding for loops in different places to see if it would work and it has not so far. Im lost on how to find specific items in the data and pull them out also.
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;
class Reader {
public static void main(String[] args) {
String abbreviation = "";
String nameOfState = "";
int population = 0;
Scanner inFile = null;
// open file
try {
inFile = new Scanner(new File("States.txt"));
} catch (FileNotFoundException e) {
System.out.println("Error: File not found");
}
// read file
System.out.printf("%-12s %5s %5s\n", "Abbreviation", "State Name",
"Pop");
System.out.printf("%-12s %5s %5s\n", "------------", "----------",
"---");
while (inFile.hasNext()) {
String record = inFile.nextLine(); // read up to new line
String[] tokens = record.split(",[ ]*");
abbreviation = tokens[0];
nameOfState = tokens[1];
population = Integer.parseInt(tokens[2]);
System.out.printf("%-12s %5s %12d\n", abbreviation, nameOfState,
population);
}
Scanner in = new Scanner(System.in);
System.out.println("Which state would you like to find?");
String question = in.nextLine();
for (int i = 0; i < abbreviation.length(); i++) {
if (question.equalsIgnoreCase(abbreviation)) {
} else {
System.out.println("Incorrect formating");
}
}
inFile.close();
}
}
--
public class States {
private String abbreviation;
private String nameOfState;
private int population;
public States(String abbreviation, String nameOfState, int population) {
super();
this.abbreviation = abbreviation;
this.nameOfState = nameOfState;
this.population = population;
}
public String getAbbreviation() {
return abbreviation;
}
public String getNameOfState() {
return nameOfState;
}
public int getPopulation() {
return population;
}
}

First let's cal the class State and not States it has no sense
Then you need to
declare a new array list List<State> stateList = new ArrayList<>();
for each line create a State instance, and add it to the list
List<State> stateList = new ArrayList<>();
while (inFile.hasNext()) {
String record = inFile.nextLine(); // read up to new line
String[] tokens = record.split(",[ ]*");
String abbreviation = tokens[0];
String nameOfState = tokens[1];
int population = Integer.parseInt(tokens[2]);
stateList.add(new State(abbreviation, nameOfState, population));
}
Then iterate over each State in the list, and if the abbrevation matches the user input : print it
Scanner in = new Scanner(System.in);
System.out.println("Which state would you like to find?");
String question = in.nextLine();
for (State state : stateList) {
if (question.equalsIgnoreCase(state.getAbbreviation())) {
System.out.println(state);
}
}
And in State class
#Override
public String toString() {
return String.format("%-12s %5s %12d", abbreviation, nameOfState, population);
}
Streamy version for fun
Using a constructor that takes the line directly
public State(String data) {
String[] tokens = data.split(",\\s*");
this.abbreviation = tokens[0];
this.nameOfState = tokens[1];
this.population = Integer.parseInt(tokens[2]);
}
You could
List<State> stateList = Files.lines(Path.of("States.txt"))
.map(State::new)
.collect(Collectors.toList());
stateList.stream()
.filter(state -> state.getAbbreviation().equals(question))
.forEach(System.out::println);

I don't know where my String index out of range: 0 error is coming from

I'm trying to take data out of a txt file and create comparable objects out of the data and add them to an array. After that array is created, I want to make a 2d array that stores a 1 in a slot if two options meet the requirements. I keep getting a String index out of range: 0 error though and I do not know where it comes from.
import java.util.*;
import java.io.*;
public class CourseScheduler
{
public int numberOfCourses;
public int[][] adjacent;
public Course[] courses;
public CourseScheduler(String filename)
{
File file = new File(filename);
try{
Scanner scan = new Scanner(file);
numberOfCourses = scan.nextInt();
courses = new Course[numberOfCourses];
adjacent = new int[numberOfCourses][numberOfCourses];
scan.useDelimiter(",|\\n");
for(int i = 0; i < numberOfCourses;i ++){
if(scan.hasNext()){
String dept = scan.next();
String num = scan.next();
String building = scan.next();
String room = scan.next();
String instruct = scan.next();
courses[i] = new Course(dept, num, building, room, instruct);
}
}
}
catch(FileNotFoundException ex){
System.out.println("File was not found");
}
for(int x = 0;x<numberOfCourses;x++){
for(int y = 0;y<numberOfCourses;y++){
adjacent[x][y] = (courses[x].compare(courses[y]));
}
}
}
This is the code for the main class
public class Course{
String department;
String courseNum;
String buildingCode;
String roomCode;
String instructorName;
public Course(String dept, String number, String building, String room, String instructor){
department = dept;
courseNum = number;
buildingCode = building;
roomCode = room;
instructorName = instructor;
}
public String getDept(){
return department;
}
public String getCourse(){
return courseNum;
}
public String getBuilding(){
return buildingCode;
}
public String getRoom(){
return roomCode;
}
public String getInstructor(){
return instructorName;
}
public String toString(){
return department + ";" + courseNum + ";" + buildingCode + ";" + roomCode + ";" + instructorName;
}
public int compare(Course comp){
int ans = 1;
String compNum = comp.getCourse();
if(instructorName == comp.getInstructor())
ans = 0;
if(buildingCode == comp.getBuilding()){
if(roomCode == comp.getRoom())
ans = 0;
}
if(department == comp.getDept()){
if(courseNum.charAt(0) == compNum.charAt(0))
ans = 0;
}
return ans;
}
}
this is the code for the course class

Educated guess: Most likely your error is coming from this line:
if(courseNum.charAt(0) == compNum.charAt(0))
ans = 0;
Either courseNum or compNum are empty.

I did not try to compile and run it but its seems that the exception comes from this line
if(courseNum.charAt(0) == compNum.charAt(0))
If a string is empty, charAt(0) will throw exactly the given exception.
Tip: if you don't know how to use a debugger, use the old fashioned System.out.println(). Put println() here and there in your code to understand how it works.

Exception Handling & IO

So I created a program that loads in a file that has the format: John 55 18.27 And then passes those three variables(once split) into a newly created file.
I get an exception error for 1) Jack Turner 44 19.22 & 2) Mike 55.0 23.44
The first error is because the last name, and another for an integer like 55.0
How can I fix my code to handle these exceptions?
import java.util.*;
import java.io.File;
import java.util.Scanner;
public class methods {
private String name;
private int hours;
private double timeSpent;
private double averageGPA;
private Scanner x;
private StringTokenizer stk;
private String[] storage = new String[11];
private Formatter file;
public void openFile(){
try{
x = new Scanner(new File("students.dat"));
}
catch(Exception e){
System.out.println("could not find file");
}
}
public void readFile(){
int count = 0;
while(x.hasNext()){
storage[count] = x.nextLine();
count ++;
}
}
public void closeFile(){
x.close();
}
public void stringTokenizer(){
int count = 0;
createNewFile();
while(count < storage.length){
stk = new StringTokenizer(storage[count]);
name = stk.nextToken();
hours = Integer.parseInt(stk.nextToken());
timeSpent = Double.parseDouble(stk.nextToken());
addRecords();
count++;
}
file.close();
}
public void createNewFile(){
try{
file = new Formatter("skeleton.txt");
}
catch(Exception e){
System.out.println("There has been an error");
}
}
public void addRecords(){
file.format("%s %s %s\n", name, hours, timeSpent);
}
}
public class Lab1_a {
public static void main(String[] args) {
int creditHrs; // number of semester hours earned
double qualityPts; // number of quality points earned
double gpa; // grade point (quality point) average
String line, name = "", inputName = "students.dat";
String outputName = "warning.dat";
//Get File
methods obj1 = new methods();
//Create an Array of Strings
obj1.openFile();
obj1.readFile();
obj1.createNewFile();
obj1.stringTokenizer();
obj1.closeFile();
}
}

First, after reading name, if the next token cannot be parsed as a double, append it to name with a space in between. Continue until you find a double.
Once you've found the first double, cast that into an int and store as hours.
ParsetimeSpent as before.
Here's some (untested) code that should get you started:
name = stk.nextToken();
String next;
while (true) {
try {
next = stk.nextToken();
hours = (int)Double.parseDouble(next);
break;
} catch (NumberFormatException e) {
name = name + " " + next;
}
}
timeSpent = Double.parseDouble(stk.nextToken());