Read the MailingListModel class (see below). In a couple of sentences, explain what each of the following methods does and be sure to explain both normal program flow and exceptional conditions. If a method calls another method, you at least need to explain what happens as the result of a method call, instead of just saying call xxx method.

• constructor
• closeDown()
• addEmail(String)
• removeEmail(String)
• getStatusMsg() and getErrorFlag()
• getAllEmails()

public class MailingListModel { private String fileName; // name of the file used to store email addresses private ArrayList < String > emailList; // list of email addresses private boolean hadError; // true if error/exception detected private String statusMsg; // last status message

//***************************************************************************************

// constructor public MailingListModel() { emailList = new ArrayList < String > (); statusMsg = "no actions"; hadError = false; // no errors fileName = "data/emails.txt";

loadFromFile(); // load data }

// close down operation: write records to file public void closeDown() { saveToFile(); }

// add a record public boolean addEmail(String emailAddress) { String entry = emailAddress.trim().toLowerCase(); // clean up

if (entry.isEmpty()) { statusMsg = "Failed to add. Please enter an email address"; hadError = true; // flag that an error just happened return false; // add failed } else if (emailList.contains(entry)) // record already exists { statusMsg = "Failed to add. This email address has already been registered"; hadError = true; // flag that an error just happened return false; // add failed } else { statusMsg = "Add succeeded"; emailList.add(entry); return true; // add was successful } }

// remove a record public boolean removeEmail(String emailAddress) { String entry = emailAddress.trim().toLowerCase(); // clean up

if (entry.isEmpty()) { statusMsg = "Failed to remove. Please enter an email address"; hadError = true; // flag that an error just happened return false; // add failed } else if (emailList.contains(entry)) // record exists { statusMsg = "Remove succeeded"; emailList.remove(entry); return true; } else { statusMsg = "Failed to remove. This email address is not registered"; hadError = true; return false; } }

// retrive error message, if any public String getStatusMsg() { return statusMsg; }

// check if any error public boolean getErrorFlag() { return hadError; }

// retrieve all emails public String[] getAllEmails() { // http://stackoverflow.com/questions/4042434/converting-arrayliststring-to-string-in-java return emailList.toArray(new String[0]); }

//***************************************************************************************

// load email addresses from text file private int loadFromFile() { Scanner fileIn = null; // scanner object to connect to file

int recordCount = 0; // track # of records

try { // open input file fileIn = new Scanner(new BufferedReader(new FileReader(fileName)));

// loop through multiple records while (fileIn.hasNext()) { // 1. read one email address String entry = fileIn.next();

// 2. add to array list emailList.add(entry.trim().toLowerCase()); recordCount++; } // end while loop } // end try block catch (IOException ioe) { statusMsg = "Error loading mailing list file: " + ioe.getMessage(); hadError = true; } // end catch block finally // close file { if (fileIn != null) { // close if was connected to a file fileIn.close(); } } // end file input

return recordCount; } // end loadFromFile

//***************************************************************************************

// write all email addresses to file private void saveToFile() { BufferedWriter writer = null; // object used to write to file try { File file = new File(fileName); // open file writer = new BufferedWriter(new FileWriter(file)); // connect object to file for (int i = 0; i < emailList.size(); i++) { writer.write(emailList.get(i)); // write one email address writer.newLine(); // write a newline character } } // end try block catch (IOException ioe) { statusMsg = "Failed to save to mailing list file: " + ioe.getMessage(); hadError = true; } // end catch block finally { // close writer file try { writer.close(); } catch (IOException ioe) { statusMsg = "Failed to close mailing list file: " + ioe.getMessage(); hadError = true; } } // end finally

} // end saveToFile

} // end class MailingListModel