我的任务是将两个类连接在一起。第一类是售票机，允许该人购买票据然后将其打印出来（通过System.out.println）。第二类是显示时间的时钟显示。
我的任务是让故障单类打印当前显示在时钟显示类中的时间。我被告知我不需要编辑NumberDisplay类或ClockDisplay类。
我的初衷是在我的ticketmachine类中创建一个新的ClockDisplay字段，然后使用
System.out.println("Time:" + ClockDisplay.displayString);
因为displayString是我用来在clockdisplay类中查找值的方法。但是，由于该字段是私有的，我无法编辑clockdisplay类，我不能这样做。有什么想法吗？
谢谢。到目前为止，这是我的代码，其中包含TicketMachine类中的上述代码。
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();
}
}
售票机
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;
}
}
答案 0 :(得分：0)
使用提供的方法getTime()来获取它。像，
System.out.println("Time:" + ClockDisplay.getTime());
另外（按照惯例），Java变量应该以小写字母开头。
ClockDisplay clockDisplay;
// Set-up the variable....
System.out.println("Time:" + clockDisplay.getTime());
答案 1 :(得分：0)
在TicketMachine课程中，您忘记了实例化ClockDisplay。请在printTicket()中的TicketMachine方法中尝试此操作：
time = new ClockDisplay();
System.out.println("Time:" + time.getTime());
<强>更新
以下是设置时间的方法：
time = new ClockDisplay();
time.setTime(3,9,34);
System.out.println("Time: " + time.getTime());
这是输出：
##################
# The BlueJ Line
# Ticket
# -2 cents.
##################
Time: 3:09:34
答案 2 :(得分：0)
如果您发现只有字段是私有的。要访问这些私有字段，您需要使用公共getter-setter方法。这是OOP的基本概念之一 - 封装。
要访问你的getter setter，你必须实例化你的对象，正如你所看到的，这些不是静态方法。
您可以在要打印时间的类中创建ClockDisplay的对象。
ClockDisplay clockDisplay = new ClockDisplay();
System.out.print(clockDisplay.getTime());