Question

For some reason everywhere in this program, my ArrayList is returning a size of 0 which really messes me up in finishing the program. I can not finish the program until I get this fixed.

Here is the program:

import java.util.*;
import java.io.*;
import java.io.File;
import java.io.FileReader;


public class Book
{
//Instance Variables
private String author;
private static String title;

/*ArrayList<Books> books = new ArrayList<Books>();*/

public static void main(String[] args) throws Exception
{       

ArrayList<String> books = new ArrayList<String>();

fillArray(books);
getBook(books);
/*  getTitle(books);

clearScreen();
getFile(books);
printMenu();
chooseOption(books);
display(books);
/*  exit();*/
}

private static void printArrayList(ArrayList<String> books)
{
for (int i = 0; i < books.size(); i++){
            System.out.println(books.get(i));
}
}

private static void fillArray (ArrayList<String> books) throws Exception
{
File file = new File("library.dat");
    BufferedReader br = new BufferedReader(new FileReader(file));
    List<String> lines = new ArrayList<String>();
    String line = br.readLine();
    while(line != null) {
        lines.add(line.replace(">", ""));
        line = br.readLine();
    }
    for(String l : lines) {
        System.out.println(l);
    }
}

public static void clearScreen()
{
    System.out.println("\u001b[H\u001b[2J");
}

private static void exit()
{
System.exit(0);
}

private static void printMenu()
{
System.out.println("\t^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^");
System.out.println("\t\tTHE GREAT BOOKS SEARCH PROGRAM");
System.out.println("\t^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^");
System.out.println("\t1) Display all book records");
System.out.println("\t2) Search for a book by Title");
System.out.println("\t3) Exit Search Program");
System.out.println("\t^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^");
 }

private static void chooseOption(ArrayList<String> books)
{
System.out.print("\tPlease Enter Your Choice > ");
Scanner stdin = new Scanner(System.in);
String option = stdin.nextLine();

if (option.compareTo("1") == 0){
    printRecord(books);
    display(books);}
else if (option.compareTo("2") == 0){
    showSearch(books, "Moby Dick");}
else if (option.compareTo("3") == 0){
    System.out.println("\n\tGoodbye. Have a nice day. :-)");
    System.exit(0);}
}

public static void printRecord(ArrayList<String> books)
{
clearScreen();
for (int i = 0; i < books.size(); i++){
System.out.println("\tRecord #" + books.get(i));}

System.out.println("\t^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^");

System.out.println("\tTitle : ");

System.out.println("\tAuthor's Name : ");

System.out.println("\tCopyright : ");

System.out.println("\tPrice : ");

System.out.println("\tGenre : ");

System.out.println("\t^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^");
System.out.println();
}

private static void display(ArrayList<String> books)
{

    Scanner in = new Scanner(System.in);

    for(int i = 0; i< books.size();i ++)
    {
        printRecord(books);
        System.out.println("");
        System.out.print("\tPress enter to continue, or type M to go back to the menu >   ");

if(in.nextLine().equals("M"))
          break;
          clearScreen();
    }
}

public static void showSearch(ArrayList<String> books, String key)
{
System.out.print("\n\tSearch Title > ");

Scanner stdin = new Scanner(System.in);
String Stitle = stdin.nextLine();

System.out.println(binarySearch(books, Stitle));
}

public static void getFile(ArrayList<String> books)
{
System.out.println("\t\tTHE BOOK SEARCH PROGRAM");
System.out.println("__________________________________________________________________        _____________");
System.out.println();
System.out.println("\tWhat file is your book data stored in?");
System.out.println();
System.out.println("\tHere are the files in the current directory : \n");

//Get all files from directory
File curDir = new File(".");
String[] fileNames = curDir.list();
ArrayList<String> data = new ArrayList<String>();

//Find files which may have data.
for(String s:fileNames)
    if(s.endsWith(".dat"))
        data.add(s);

for (int i = 0; i < data.size(); i++){
            System.out.println(data.get(i));
}

System.out.print("\n\tFilename: ");

Scanner stdin = new Scanner(System.in);
String dataName = stdin.nextLine();

int arraysize = books.size();
if (dataName.equals("library.dat")){
    Collections.sort(books);
    System.out.println("\n\tA total of " + arraysize + " have been input & sorted by title.");}
else {
    System.out.println("Error");}

System.out.print("\n\tPlease Hit Return to Continue...");
Scanner stdin2 = new Scanner(System.in);
String st = stdin2.nextLine();
clearScreen();
}

public static void getBook(ArrayList<String> books) throws Exception
{
int totalElements = books.size();

//  while (dataScanner.hasNext())
File datafile = new File("library.dat");
Scanner datascanner = new Scanner (datafile);
String data = datascanner.nextLine();
StringTokenizer dataParser = new StringTokenizer(data, ";");
title = dataParser.nextToken();
String author = dataParser.nextToken();  
    String   CopyR = dataParser.nextToken();
    String Price = dataParser.nextToken();
String Genre = dataParser.nextToken();

System.out.println(totalElements);
for (int i=0; i< books.size(); i++){
System.out.println(title);
System.out.println(author);
System.out.println(CopyR);
System.out.println(Price);
System.out.println(Genre);
}
}

public static String getTitle(ArrayList<String> books) throws Exception
{
String n = "n";
    for (String str : books)
{
  StringTokenizer st = new StringTokenizer(str, ";");
  String title = st.nextToken();
}
    return title;   
}

private static int binarySearch (ArrayList<String> books, String key)
{
Collections.sort(books);
int index = Collections.binarySearch(books, key);

return index;
}



/*
public Book (String title, String author, String CopyR, String Price)
{
this.title = title;
this.author = author;
this.CopyR = CopyR;
this.Price = Price;
}
*/
}

Answer 1

The answer is the obvious one: you never call books.add() or books.addAll(). Not once.

I think you meant to implement fillArray something like this instead:

private static void fillArray (ArrayList<String> books) throws Exception
{
    File file = new File("library.dat");
    BufferedReader br = new BufferedReader(new FileReader(file));
    String line = br.readLine();
    while(line != null) {
        books.add(line.replace(">", ""));
        line = br.readLine();
    }
}