Two problems with two different classes.

Question

im having two problems: i get nothing with the printConferences() method inside ReferenceBook class, the arraylist size is equal to zero. and my printSchoolsAndCopies() and schoolsAndCopiesToArray() methods which are inside TextBook class, give exceptions:
Exception in thread "main" java.lang.ArrayStoreException at java.lang.System.arraycopy(Native Method) at java.util.ArrayList.toArray(ArrayList.java:304) at project3.TextBook.schoolsAndCopiesToArray(TextBook.java:64) at project3.TextBook.printSchoolsAndCopies(TextBook.java:74) at project3.BookTester.main(BookTester.java:27) Java Result: 1 BUILD SUCCESSFUL (total time: 0 seconds)
all you need to read is TextBook and ReferenceBook class, but i added the tester and BookCatalog, which is an arraylist of books.
here are my TextBook and ReferenceBook classes and the tester, there are two abstract classes Book and TechnicalBook, but i wont post them unless anybody needs them, i presume not.
* TextBook.java
* Created on April 19, 2007, 8:02 PM
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
package project3;
import java.util.*;
* @author Kevin
public class TextBook extends TechnicalBook{
    private ArrayList <String> schools;
    private ArrayList <Integer> numberCopiesForSchool;
    private String [][] schoolsAndCopies;
    public static final String TEXTBOOK = "Textbook";
    /** Creates a new instance of TextBook */
    public TextBook(String author, String title, int numberPages, int copiesSold,
            double price) {
        super(author, title, numberPages, copiesSold, price);
        schools = new ArrayList();
        numberCopiesForSchool = new ArrayList();
    public int getNumberCopiesForSchool(String school){
        Integer temp = null;
        for(int i = 0; i < schools.size();i++){
            if(schools.get(i).equals(school))
               temp = numberCopiesForSchool.get(i);
        return temp;
    public void addSchool(String school){
        Integer one = new Integer(1);
        schools.add(school);
        // number of copies for the school is initially 1
        numberCopiesForSchool.add(one);  
    public int getNumberSchools(){
        int count = 0;
        for(int i = 0; i < schools.size(); i++){
            if(schools.get(i) != null)
                count++;
        return count;
    public void addCopiesForSchool(String school, int copies) {
          for (int i = 0; i < schools.size(); i++) {
                    if (schools.get(i).equals(school))
               numberCopiesForSchool.set(i, numberCopiesForSchool.get(i)
                            + (Integer) copies);
    private void schoolsAndCopiesToArray(ArrayList <String> a, ArrayList <Integer> b){
        String [] c = null;
        String [] d = null;
        c = (String[]) a.toArray(new String[a.size()]);
        d = (String[]) b.toArray(new String[b.size()]);
        String [] [] schoolsAndCopies = null;
        for(int i = 0; i < c.length;i++){
            for(int j = 0; j < d.length;j++){
                schoolsAndCopies[i] = c;
                schoolsAndCopies[j] = d;
    public void printSchoolsAndCopies(String title){
        schoolsAndCopiesToArray(schools, numberCopiesForSchool);
        System.out.println("---------------");
        System.out.println("Schools and copies sold to each school for " + this.title+ ".");
        System.out.println("Schools:\tCopies:");
        for(int i = 0; i < schoolsAndCopies.length;i++)
            for(int j = 0; j < schoolsAndCopies.length;j++)
System.out.println(schoolsAndCopies [i] + "\t" +
schoolsAndCopies[j]);
public String getClassName(){
return TEXTBOOK;
// overrides TechnicalBook toString
public String toString(){
return "Author = " + author + ". Title = " + title + ". Number of Pages = " +
numberPages + ". Copies Sold = " + copiesSold + ". Schools using " + title +
". Price = " + this.getPrice() + " = " + this.getNumberSchools() + ". ";
* ReferenceBook.java
* Created on April 19, 2007, 8:02 PM
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
package project3;
import java.util.*;
* @author Kevin
public class ReferenceBook extends TechnicalBook{
private ArrayList <String> conferences;
public static final String REFERENCE_BOOK = "Reference Book";
//private int numberConferences;
/** Creates a new instance of ReferenceBook */
public ReferenceBook(String author, String title, int numberPages, int copiesSold,
double price) {
super(author, title, numberPages, copiesSold, price);
conferences = new ArrayList();
public String getConference(int a){
for(int i = 0; i < conferences.size();i++)
if(i == a)
return conferences.get(i);
return null;
public void addConference(String conference){
for(int i = 0; i < conferences.size();i++){
conferences.add(conference);
break;
public void printConferences(){
System.out.println("-------------");
System.out.println("Conferences made for " + this.title + ".");
for(int i = 0; i < conferences.size(); i++){
System.out.println("["+(i + 1) +"]: "+ conferences.get(i));
System.out.println(conferences.size());
public String getClassName(){
return REFERENCE_BOOK;
public String toString(){
return super.toString();
* BookTester.java
* Created on April 19, 2007, 8:02 PM
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
package project3;
* @author Kevin
public class BookTester{
/** Creates a new instance of BookTester */
public static void main(String [] args){
BookCatalog catalog = new BookCatalog("Library");
TextBook java = new TextBook("John", "Java", 5, 20, 5.00);
TextBook beans = new TextBook("Mike", "JavaBeans", 6, 21, 5.00);
ReferenceBook ref = new ReferenceBook("Jones", "Standard Class Library", 6, 23, 5.00);
ref.addConference("Meeting");
ref.printConferences();
beans.addSchool("UTSA");
beans.printSchoolsAndCopies("c++");
catalog.addBook(java);
catalog.addBook(beans);
catalog.printCatalog();
my BookCatalog class is fine, and everything prints out with out using the listed methods that give trouble.
* BookCatalog.java
* Created on April 20, 2007, 4:42 PM
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
package project3;
import java.util.*;
* @author Kevin
public class BookCatalog {
    private String name;
    private ArrayList <Book> bookList;
    /** Creates a new instance of BookCatalog */
    public BookCatalog(String name) {
        this.name = name;
        bookList = new ArrayList <Book>();
    public String getCatalogName(){
        return name;
    public void addBook(Book b){
        bookList.add(b);
    public void printCatalog(){
        for(int i = 0; i < bookList.size(); i ++){
            System.out.println("[" + i + "]: " + bookList.get(i).getClassName() +
                   ": " + bookList.get(i).toString());
}thanks in advance

Answer 1

everything runs now, but it doesnt sort them. it prints them in the original order: here is the revised BookCatalog and Tester, also when making sortByTitle static it gives non static variable errors so i have no idea. Thanks for helping me fix the errors, i have no idea why it doesnt sort.
* BookCatalog.java
* Created on April 20, 2007, 4:42 PM
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
package project3;
import java.util.*;
* @author Kevin
public class BookCatalog {
    private String name;
    private ArrayList <Book> bookList;
    //private Book [] bookList2;
    /** Creates a new instance of BookCatalog */
    public BookCatalog(String name) {
        this.name = name;
        bookList = new ArrayList <Book>();
    public String getCatalogName(){
        return name;
    public void addBook(Book b){
        bookList.add(b);
        public void sortByTitle(ArrayList<Book> list){
      if (bookList.size() > 1)
        for (int index = 1; index < bookList.size(); index++)
           insertItemByTitle(bookList, index);
     private void insertItemByTitle(ArrayList <Book> bookList, int index) {
            Book key = bookList.get(index);
            int position = index;
            while (position > 0 && key.getTitle().compareTo(bookList.get(index).getTitle()) < 0)   {
                bookList.set(position, bookList.get(position-1));// = bookList.set(position-1, key);
               position--;
            bookList.set(position, key);
    public void printCatalog(){
        sortByTitle(bookList);
        Book [] bookList2 = (Book[])bookList.toArray(new Book[bookList.size()]);
        for(int i = 0; i < bookList2.length; i ++){
            System.out.println("[" + (i+1) + "]: " + bookList2.getClassName() +
": " + bookList2[i].toString());
* BookTester.java
* Created on April 19, 2007, 8:02 PM
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
package project3;
* @author Kevin
public class BookTester{
/** Creates a new instance of BookTester */
public static void main(String [] args){
BookCatalog catalog = new BookCatalog("Library");
TextBook java = new TextBook("John", "Java", 5, 20, 5.00);
TextBook beans = new TextBook("Mike", "JavaBeans", 6, 21, 5.00);
ReferenceBook ref = new ReferenceBook("Jones", "Standard Class Library", 6, 23, 5.00);
ref.addConference("Meeting");
ref.printConferences();
beans.addSchool("UTSA");
//beans.printSchoolsAndCopies("c++");
catalog.addBook(ref);
catalog.addBook(java);
catalog.addBook(beans);
catalog.printCatalog();