CommandLineCalculator-NON-ROBUST

// NON-ROBUST IMPLEMENTATION: CRASHES AT MOST USER ERRORS

import java.io.*;
import java.util.*;

/**
 * Performs addition from the command line on multiple accounts.
 */

class CommandLineCalculator
{
    private int accumulatedValue = 0;   // affected by arithmetic operation(s) on this
    private static Vector calculators = new Vector();   // the accounts active in this session

/*****************************************************************************************************
 */
public CommandLineCalculator()
/*****************************************************************************************************/
{   super();
}

/*****************************************************************************************************
 * Postconditions:
 * (1) Application has obtained number of accounts from user
 * (2) Application has prompted user to add integers to any of these accounts
 * (3) Application has output to console the balance after each transaction
 */
public static void main( String[] args )
/*****************************************************************************************************/
{
    solicitNumberAccounts();
    interactWithUser();
    System.out.println( "\n\t---- Application ends. ----" );
}

/*****************************************************************************************************
  * Preconditions: this.accumulatedValue == 0
  *
  * Postconditions:
  * (1) The user has been prompted to add a sequence of integers or "stop" to quit
  * (2) The user has responded with a sequence of integers or "stop"
  * (3) The console has echoed each integer added and the accumulating total
  * (4) The application has ended after the user has entered "stop"
  * (5) 'accumulatedValue' contains the total of all integers entered since the application began
  * (6) The application has stated "Please enter an integer only." whenever the user has
  *     entered a non-integer, and allowed re-entry.
  */
protected void executeAdditions()
/*****************************************************************************************************/
{
    // Get amount to add
    System.out.println
     ( "\tPlease enter the amount you want added, or type 'stop' to stop adding for now: " );
    String userRequest = getAnInputFromUser();

    // Add the amount if valid until "stop" entered
    int amountAdded = 0;
    while( !userRequest.equals( "stop" ) )
    {
        amountAdded = ( new Integer( userRequest ) ).intValue();
        this.accumulatedValue += amountAdded;
        System.out.println
             ( "\tAdded " + amountAdded + ", getting total of " + this.accumulatedValue );
        System.out.println
         ( "\tPlease enter the amount you want added, or type 'stop' to stop adding for now: " );
        userRequest = getAnInputFromUser();
    }

    System.out.println( "\tAddition ends." );

}   // end executeAdditions()



/*****************************************************************************************************
 * Precondition: 'CommandLineCalculator.calculators' not null.
 * Postconditions:
 * (1) The application has prompted the user for a number of accounts
 * (2) The user has complied legitimately
 * (3) 'CommandLineCalculator.calculators' contains one 'CommandLineCalculator' object
 *     for each desired account, each initialized to zero.
 */
private static void solicitNumberAccounts()
/*****************************************************************************************************/
{
    int numAccounts = 0;

    // Get the number of accounts
    System.out.println( "\n=========== How many accounts do you want to open: ===========" );
    numAccounts = ( new Integer( getAnInputFromUser() ) ).intValue();
    System.out.println   // echo
     ( "The application will deal with " + numAccounts + " accounts.\n" );

    // Establish the accounts
    for( int accountIndex = 0; accountIndex < numAccounts; ++accountIndex )
        CommandLineCalculator.calculators.addElement( new CommandLineCalculator() );

}   // end solicitNumberAccounts()

/*****************************************************************************************************
 * Postconditions: the user has been prompted for a string
 * Return: String input by user if the user provides one, otherwise one blank
 */
private static String getAnInputFromUser()
/*****************************************************************************************************/
{
    try
    {   BufferedReader b = new BufferedReader( new InputStreamReader( System.in ) );
        return ( b.readLine() );
    }
    catch( IOException e )
    {   System.out.println( e + " Input taken to be a single blank." );
        return " ";
    }
}

/*****************************************************************************************************
 */
public static void interactWithUser()
/*****************************************************************************************************/
{
    // Get the account
    String userRequest = " ";

    do   // as long as user does not signal desire to end the interaction
    {
        // Get the next account requested by the user
        System.out.println
         ( "\n---------- Please enter account number (starting at 1) or 'Quit application': -----------" );
        userRequest = getAnInputFromUser();
        if( userRequest.equals( "Quit application" ) )
            break;

        // Get the account and perform operations on it
        int accountNum = ( new Integer( userRequest ) ).intValue() - 1;
        CommandLineCalculator cLC =
         (CommandLineCalculator)( calculators.get( accountNum ) );
        // Report on balance
        System.out.println( "\tThe balance in this account is " + cLC.accumulatedValue + "\n");
        cLC.executeAdditions();
    }
    while( !userRequest.equals( "Quit application" ) );

}   // end interactWithUser()

}