Class MessageLoader

Object

MessageLoader

public class MessageLoader
extends Object

This utility class contains methods that will read in a file as it is provided, and load the data into an ArrayList with OpenMessage objects inside of it.

Constructor Summary

Constructors

Constructor	Description
MessageLoader()

Method Summary

Modifier and Type	Method	Description
static ArrayList<OpenMessage>	loadFile(String filename)	This method reads through a file, and builds a number of Message objects based on the contents of that file.
static String	parseLine(String line)	Takes in a line, in which one must grab the substring *after* the ":".

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

MessageLoader

public MessageLoader()

Method Details

loadFile

public static ArrayList<OpenMessage> loadFile(String filename)

This method reads through a file, and builds a number of Message objects based on the contents of that file. It then returns an ArrayList for each Message.

For this file, you can assume the following format:

      TO: name
      FROM: name
      SUBJECT: short subject
      BODY: single line message, no need to worry about \n
 

Every four lines will be there, and they will be setup in sets of four. As such, *if* a line exists, you can assume four lines.

For example:

      TO: Alice
      FROM: Hatter
      SUBJECT: Red Queen
      BODY: To keep ahead, run from the red queen.
      TO: Hatter
      FROM: Red
      SUBJECT: New Hat
      BODY: Hatter, I need a new hat, and if I don't get it, you won't need one. *Kisses* Queen.
 

Implementation Suggestions

First make sure to initialize the arraylist, and just return the empty list. I would suggest compiling at that point just to make sure you don't have a typo.

Second, work through reading the file. It will be a loop that loops until there are no more lines. Scanner.hasNextLine()

Remember, when you read the file, you can assume four lines at a time. Here is some sample code to help you.

      // while inside the loop, that loops *while* scanner.hasNextLine()...
     String to = parseLine(scanner.nextLine());
     String from = parseLine(scanner.nextLine());
     // some of your code here to complete this
     messageList.add(new OpenMessage(to, from, sub, body)); // assuming I called my ArrayList messageList

 

Be aware of the other supporting methods we are having you implement (hint, implement and test them first!). Also remember that when scanning from a file, use a try/catch block. If there is no error, catch the FileNotFoundException!

Parameters:

filename - Name of file to be opened.

Returns:

An ArrayList of type Message with 0 or more messages.

parseLine

public static String parseLine(String line)

Takes in a line, in which one must grab the substring *after* the ":". It will also remove any leading and trailing spaces.

Implementation Hints:

• Use indexOf(), but don't forget to double check that it works due to OB1 errors! String.indexOf(String)
• Use String.trim() after you get the substring!
• String.substring(int) will prove helpful.

Notice we are focusing on divide conquer glue. This allows us to test parseLine() before we even have to worry about reading a file!

Parameters:

line - line to substring and trim

Returns:

parsed line