reading input from a file into a array

[John Saito]

hello, i am trying to read a list of names from a .txt file into a array when the program starts. I am completly stuck on this. this is the code is have so far but no matter what i try its not working. please help.

import java.util.*;
import java.io.*;
 
public class Project2
{
private static int MAX_LIST_LENGTH = 10;
private static OneWayNoRepeatsList toDoList = new OneWayNoRepeatsList(MAX_LIST_LENGTH);   // creating toDoList
 
private static void DisplayCustomerList()
{
    Scanner keyboard = new Scanner(System.in);  // uses Scanner for reading
    
System.out.println("");
System.out.println("****** CUSTOMER DATABASE: VIEW LIST ******");
System.out.println("");
if (toDoList.empty())
{
System.out.println("The customer list is currently empty.");
}
else
{
System.out.println("Customers:");   // writing out entire toDoList
 
int position = toDoList.START_POSITION;
String next = toDoList.getEntryAt(position);
while (next != null)    //  null indicates end of list
{
System.out.println(position + ".\t" + next);
position++;
next = toDoList.getEntryAt(position);
}
System.out.println("Total customers:" + (position-1));
}

    System.out.println("");
    System.out.println("Press Enter to return to the menu");
String next = keyboard.nextLine();
}
 
private static void AddCustomersToList()
{
    Scanner keyboard = new Scanner(System.in);  // uses Scanner for reading
 
System.out.println("");
System.out.println("****** CUSTOMER DATABASE: ADD CUSTOMERS ******");
System.out.println("");
 
if (toDoList.full())
    {
System.out.println("List is currently full");
    }
    else
    {
System.out.println("When prompted, enter customer names to be added to the list");
System.out.println("");
 
boolean more = true;
 
while ( more && (! toDoList.full( )))   
{
System.out.println("Customer Name? ");
String next = "";
while (next.length() == 0)
{
next = keyboard.nextLine( ); 
}
 
if (toDoList.onList(next))
{
System.out.println(next + " is already in the customer list.");
}
else
{
toDoList.addItem(next);
System.out.println("Successfully added " + next + " to the customer list.");
}
 
if (toDoList.full( ))
{
System.out.println("List is now full.  Press Enter to return to the menu.");
next = keyboard.nextLine();
}
else
{
System.out.println("Add more customers? (\"yes\" or \"no\") ");
String ans = keyboard.nextLine();
if (ans.trim().equalsIgnoreCase("no"))
more = false;
}
}
    }
}
 
private static int FindCustomerNameIndex(String strName)
{
    int iIndex = -1;
 
    int position = toDoList.START_POSITION;     
    String next = toDoList.getEntryAt(position);
 
    boolean bFoundName = false;
boolean bEndOfList = false;
    while ((!bFoundName) && (!bEndOfList))    //  null indicates end of list
    {
if ((next != null) && (next.equalsIgnoreCase(strName)))
{
bFoundName = true;
iIndex = position;
}

if (toDoList.atLastEntry(position))
{
bEndOfList = true;
}
else
{
position++;
next = toDoList.getEntryAt(position);
}
    }
 
    return iIndex;
}
 
private static void DeleteCustomersFromList()
{
    Scanner keyboard = new Scanner(System.in);  // uses Scanner for reading
    
System.out.println("");
System.out.println("****** CUSTOMER DATABASE: DELETE CUSTOMERS ******");
System.out.println("");
 
if (toDoList.empty())
    {
System.out.println("List is currently empty");
    }
    else
    {
System.out.println("When prompted, enter customer names to be deleted from the list");
System.out.println("");
 
boolean more = true;
 
while (more && (!toDoList.empty()))   
{
System.out.println("Customer Name? ");
String next = keyboard.nextLine();  
 
int iCustomerPosition = FindCustomerNameIndex(next);
if (iCustomerPosition == -1)
{
System.out.println("Unable to find " + next + " in the list.");
}
else
{
toDoList.deleteItem(iCustomerPosition);
System.out.println("Successfully deleted  " + next + " from the list.");
}
 
if (toDoList.empty( ))
{
System.out.println("List is empty.");
}
else
{
System.out.println("Delete more customers? (\"yes\" or \"no\") ");
String ans = keyboard.nextLine();
if (ans.trim().equalsIgnoreCase("no"))
more = false;
}
}
    }
}
 
private static void FindCustomersInList()
{
    Scanner keyboard = new Scanner(System.in);  // uses Scanner for reading
    
System.out.println("");
System.out.println("****** CUSTOMER DATABASE: FIND CUSTOMERS ******");
System.out.println("");
 
if (toDoList.empty())
    {
System.out.println("List is currently empty");
    }
    else
    {
System.out.println("When prompted, enter customer names to be searched for in the list");
 
boolean more = true;
 
while (more)
{
System.out.println("Customer Name? ");
String next = keyboard.nextLine();  
 
int iCustomerIndex = FindCustomerNameIndex(next);
if (iCustomerIndex == -1)
{
System.out.println("Unable to find " + next + " in the list.");
}
else
{
System.out.println(next + " is in the list at position: " + iCustomerIndex);
}
 
System.out.println("Search for more customers? (\"yes\" or \"no\") ");
String ans = keyboard.nextLine( );
if (ans.trim().equalsIgnoreCase("no"))
more = false;
}
    }
}

private static void saveRecords()
{
PrintWriter outputStream = null;
try 
{
outputStream = new PrintWriter(new FileOutputStream("Customer List.txt"));
}
catch(FileNotFoundException e)
{
System.out.println("Error opening file Customer List.txt");
System.exit(0);
}
{
outputStream.println(next[0]);
}
outputStream.close();
System.out.println("Those customers were written to Customer List.txt");
}

private static void customerList()
{
try
{
BufferedReader inputStream = new BufferedReader(new FileReader("List.txt")); 
String line = null;
line = inputStream.readLine();
System.out.println("First Name is: ");
System.out.println(line);
inputStream.close();
}
catch(FileNotFoundException e)
{
System.out.println("File not Found");
}
catch(IOException e)
{
System.out.println("Error reading from file ");
}
}

public static void main(String[] args)
{
    Scanner keyboard = new Scanner(System.in);  // uses Scanner for reading
    
    // loop until the user says to exit
    boolean bExit = false;
    while (!bExit)
    {
System.out.println("****** CUSTOMER DATABASE: MAIN MENU ******");
System.out.println("");
System.out.println("What would you like to do?");
System.out.println("1. View customer list");
System.out.println("2. Add customer(s) to list");
System.out.println("3. Delete customer(s) from list");
System.out.println("4. Search for customer(s)");
System.out.println("5. load customer(s) file");
System.out.println("6. Save customer(s) to file");
System.out.println("7. Exit");
 
//get choice from user
int menuChoice = keyboard.nextInt( );
switch (menuChoice)
{
case 1:
DisplayCustomerList();
break;
case 2:
AddCustomersToList();
break;
case 3:
DeleteCustomersFromList();
break;
case 4:
FindCustomersInList();
break;
case 5:
customerList();
break;
case 6:
saveRecords();
break;
case 7:
System.out.println("Thank you for using SwainCo Software.  Goodbye.");
bExit = true;
break;
default:
System.out.println("Invalid entry");
break;
}
    }
}
}    

any help is greatly appriciated.

[Michael Dunn]

your program opens, you select option 5 to load the customer/s file
and this is where you are stuck.

if this is correct,
1) if the customer data is saved into a file then you should be creating a Customer object
2) it probably would be better to use an ArrayList rather than an array,
so you can easily add new Customers. If the customers are to have a CustomerID,
a HashMap would be better

this is roughly the changes to your code

  private static void customerList()
  {
    try
    {
      BufferedReader inputStream = new BufferedReader(new FileReader("List.txt")); 
      String line = null;
      while((line = inputStream.readLine()) != null)//loops until eof
      {
        //break the line into individual bits via the delimeter it is saved as
        //Create a new Customer object from the 'bits'
        //add the new Customer to the arraylist/hashmap
      }//loop
      inputStream.close();
    }
    catch(FileNotFoundException e)
    {
      System.out.println("File not Found");
    }
    catch(IOException e)
    {
      System.out.println("Error reading from file ");
    }
  }         

to get this to work, create a class Variable
Map customers = new HashMap();

create up a Customer class

class Customer
{ 
  String name;
  String address;
  String ID;
  public Customer(String n,String a, String i)
  {
    name = n; address = a; ID = i;
  }
}

you need to break up the customer's data from the file (after reading it into 'line')
String's split() will do that for you - it returns an array
eg
String[] bits = line.split("\\|");\\where "\\|" is a regex for '|', a common delimeter

Creating the customer object
Customer cust = new Customer(bits[0],bits[1],bits[2]);
(probably would check bits.length to ensure it is = 3)

add the customer object to the hashmap
customers.put(bits[2],cust);//where bits[2] is the customersID, or 'key' for the hashmap

put it all together and you should have it

[Layne Lund]

If Michael's comments don't completely fix your problems, please tell us what you mean by "it doesn't work". Does the above code compile? If not, what are the errors? I guess I could take the time to compile it, but even then I'm not entirely sure what is supposed to happen when I run it. This is the part that you need to describe the most. What does your program actually do? In other words what happens when you run it? And how does this differ from what you expect? I think this last is the key part for us to be able to help you. Please provide as much detail as you can so we can offer suggestions that might fix it. Otherwise, we will just have to guess at what you intend which wastes your time as much as it does ours.

Layne

[John Saito]

thanks for the help so far. what i am trying to do is, to get this program to read in any names stored in a txt file (Customer List.txt) and insert them into the array. this program will allow users to add to a list, search the list for a name and delete from the list. I want to add to it buy being able to save and read from a file. It would be better if the program could read the file automatically when it is first ran. hope this clears up what i am trying to do.

[Layne Lund]

Originally posted by John Saito:
thanks for the help so far. what i am trying to do is, to get this program to read in any names stored in a txt file (Customer List.txt) and insert them into the array. this program will allow users to add to a list, search the list for a name and delete from the list. I want to add to it buy being able to save and read from a file. It would be better if the program could read the file automatically when it is first ran. hope this clears up what i am trying to do.

Okay, that helps. However, we also need to know what the program ACTUALLY does. Perhaps you can describe what you do to run the program. It looks like you provide a menu to the user. Which of these choices causes the problems? Details such as these will help you (and us) to understand which parts of your code you need to focus on.

Layne

[John Saito]

the original program was a database program which keeps track of customers. Right now customer names is the only required field. the program can add, delete, search and list all records (names). There are 2 other classes that go along with this program. (sortString, OneWayNoRepeatList) all of this works just fine, what I am trying to add to the program the ability to save/read all records to a .txt file. I created 2 methods, CustomerList and saveRecords. customerList is where i want the program to read all records into the program (array) so that if a user chooses option 1, all records will be listed, including what is in the .txt file. Then if the user chooses to save, the entire list is saved to the .txt file. I dont need the option 5, which was to load the file.

[John Saito]

this is the code i have to read from the file:

private static void customerList()
{
try
{
BufferedReader inputStream = new BufferedReader(new FileReader("List.txt")); 
String line = null;
line = inputStream.readLine();
System.out.println("First Name is: ");
System.out.println(line);
inputStream.close();
}
catch(FileNotFoundException e)
{
System.out.println("File not Found");
}
catch(IOException e)
{
System.out.println("Error reading from file ");
}
}    

I know its not complete but im clueless where to go from here.

this is the code for saving the list to a .txt.:

private static void saveRecords()
{
PrintWriter outputStream = null;
try 
{
outputStream = new PrintWriter(new FileOutputStream("Customer List.txt"));
}
catch(FileNotFoundException e)
{
System.out.println("Error opening file Customer List.txt");
System.exit(0);
}
{
outputStream.println(next[0]);
}
outputStream.close();
System.out.println("Those customers were written to Customer List.txt");
}    

this outputs "OneWayNoRepeatsList@757aef" in the text file. how do i get the records that are stored in the array to save into the file.

[Layne Lund]

It looks like you are trying to write to the file with

outputStream.println(next[0]);

What is this variable called next? Apparently it is an array, but an array of what? From the output you recieve I guess it is an array of OneWayNoRepeatsList objects. What does this class do? From the name, I can only guess that it is a list of some kind? Does it store a list of Customer objects or something similar? If this is the case, then why do you have an array of these lists? Do you need to keep multiple customer lists? This is just something to think about even though it's not related to your exact question.

So assuming that OneWayNoRepeatsList is a list of Customer objects, you need to figure out how to iterate through the Customers in the list. In other words, you need to get one Customer at a time and write it to the file. For each Customer object, you will need to get the data that you want to write to the file. It sounds like you will need at least one loop here. You might also want to find a way to break this up into a couple of different methods. For example, one method might write a single Customer object to a given OutputStream. Then another method will repeatedly call the first method with different Customer objects.

Does this help at all? Let us know how things work out for you.

Layne