I have been tasked with linking two classes together. The first class is a ticket machine which allows the person to buy a ticket and then print it out (via System.out.println). The second class is a clock display which displays the time.
My task is to make the ticket class print the time currently displayed in the clock display class. I have been told I do not need to edit either the NumberDisplay class or the ClockDisplay class.
My initital thoughts were to create a new ClockDisplay field within my ticketmachine class, and then use
System.out.println("Time:" + ClockDisplay.displayString);
as displayString is what I use to find the value within the clockdisplay class. However, as the field is private and I cannot edit the clockdisplay class, I cannot do this. Any thoughts?
Thank you. Here is my code so far, with the aforementioned piece of code in the TicketMachine class.
NumberDisplay
public class NumberDisplay
{
private int limit;
private int value;
/**
* Constructor for objects of class NumberDisplay.
* Set the limit at which the display rolls over.
*/
public NumberDisplay(int rollOverLimit)
{
limit = rollOverLimit;
value = 0;
}
/**
* Return the current value.
*/
public int getValue()
{
return value;
}
/**
* Return the display value (that is, the current value as a two-digit
* String. If the value is less than ten, it will be padded with a leading
* zero).
*/
public String getDisplayValue()
{
if(value < 10) {
return "0" + value;
}
else {
return "" + value;
}
}
/**
* Set the value of the display to the new specified value. If the new
* value is less than zero or over the limit, do nothing.
*/
public void setValue(int replacementValue)
{
if((replacementValue >= 0) && (replacementValue < limit)) {
value = replacementValue;
}
}
/**
* Increment the display value by one, rolling over to zero if the
* limit is reached.
*/
public void increment()
{
if ((value +1) >= limit) {
value = 0;
}
else {
value = value + 1;
}
}
}
ClockDisplay
public class ClockDisplay
{
private NumberDisplay hours;
private NumberDisplay minutes;
private NumberDisplay seconds;
private String displayString; // simulates the actual display
/**
* Constructor for ClockDisplay objects. This constructor
* creates a new clock set at 12:00:00.
*/
public ClockDisplay()
{
hours = new NumberDisplay(12); // changed from 24hour to 12 hour
minutes = new NumberDisplay(60);
seconds = new NumberDisplay(60);
updateDisplay();
}
/**
* Constructor for ClockDisplay objects. This constructor
* creates a new clock set at the time specified by the
* parameters.
*/
public ClockDisplay(int hour, int minute, int second)
{
hours = new NumberDisplay(12); //changed from 24hour to 12 hour
minutes = new NumberDisplay(60);
seconds = new NumberDisplay(60);
setTime(hour, minute, second);
}
/**
* This method should get called once every minute - it makes
* the clock display go one minute forward.
*/
public void timeTick()
{
minutes.increment();
if(minutes.getValue() == 0) { // it just rolled over!
hours.increment();
}
updateDisplay();
}
/**
* Set the time of the display to the specified hour and
* minute and second.
*/
public void setTime(int hour, int minute, int second)
{
if (hour == 12) { //changing the display from '00:00' to '12:00'
hour = 0;
}
hours.setValue(hour);
minutes.setValue(minute);
seconds.setValue(second);
updateDisplay();
}
/**
* Return the current time of this display in the format HH:MM:SS.
*/
public String getTime()
{
return displayString;
}
/**
* Update the internal string that represents the display.
*/
private void updateDisplay()
{
int hour = hours.getValue(); //changes the display to from showing '00:00' to '12:00'
if (hour == 0) {
hour = 12;
}
displayString = hour + ":" +
minutes.getDisplayValue() + ":" + seconds.getDisplayValue();
}
}
Ticket Machine
public class TicketMachine
{
// The price of a ticket from this machine.
private int price;
// The amount of money entered by a customer so far.
private int balance;
// The total amount of money collected by this machine.
private int total;
// The time from the clockdisplay class
private ClockDisplay time;
/**
* Create a machine that issues tickets of the given price.
*/
public TicketMachine(int cost)
{
price = cost;
balance = 0;
total = 0;
}
/**
* @Return The price of a ticket.
*/
public int getPrice()
{
return price;
}
/**
* Return The amount of money already inserted for the
* next ticket.
*/
public int getBalance()
{
return balance;
}
/**
* Receive an amount of money from a customer.
* Check that the amount is sensible.
*/
public void insertMoney(int amount)
{
if(amount > 0) {
balance = balance + amount;
}
else {
System.out.println("Use a positive amount rather than: " +
amount);
}
}
/**
* Print a ticket if enough money has been inserted, and
* reduce the current balance by the ticket price. Print
* an error message if more money is required.
*/
public void printTicket()
{
if(balance >= price) {
// Simulate the printing of a ticket.
System.out.println("##################");
System.out.println("# The BlueJ Line");
System.out.println("# Ticket");
System.out.println("# " + price + " cents.");
System.out.println("##################");
System.out.println();
// Update the total collected with the price.
total = total + price;
// Reduce the balance by the prince.
balance = balance - price;
// Print the current time from the NumberDisplay class.
System.out.println("Time:" + ClockDisplay.displayString);
}
else {
System.out.println("You must insert at least: " +
(price - balance) + " more cents.");
}
}
/**
* Return the money in the balance.
* The balance is cleared.
*/
public int refundBalance()
{
int amountToRefund;
amountToRefund = balance;
balance = 0;
return amountToRefund;
}
}
Use the provided method
getTime()to get it. Like,Also (by convention), Java variables should start with a lower-case letter.