这是我的问题，如果（carMinutesPaid＆gt; meterMinutesPaid），我似乎无法弄清楚如何调用ParkingTicket对象？这里有任何人可以帮助解决问题。
public static ParkingTicket checkParking(int carMinutesParked, int meterMinutesPaid)
{
Car parker = carMinutesParked;
ParkingMeter parkee = parkee;
if(carMinutesParked>meterMinutesPaid){
return new ParkingTicket(parker, parkee);
}
else if(carMinutesParked<=meterMinutesPaid){
System.out.println("null");
}
return new ParkingTicket(parker, parkee);
}
这是我的项目的问题。
请记住，此方法必须能够在没有ParkingTicket对象的情况下使用。
Car参数和ParkingMeter参数，确定是否应创建ParkingTicket对象。ParkingTicket(parker, parkee)，并返回结果。null。这是我的车类：
/**
* This is a Car class for Impark.
*
* @author Tre
* @version 2.0 15 October 2015
*/
public class Car
{
private static final int MINIMUM_PLATE_LENGTH=2;
private static final int MAXIMUM_PLATE_LENGTH=7;
public static final char MANUAL_TRANSMISSION='m';
public static final char AUTOMATIC_TRANSMISSION='a';
private static int defaultMinutesParked = 0;
private static double defaultOdometerInKm = 50000.5;
private String licensePlate;
private char transmissionType;
private double odometerInKm;
private int minutesParked;
/**
* @param newProposedLicensePlate the license plate of the car can equal null
* but must be between MINIMUM_PLATE_LENGTH and MAXIMUM_PLATE_LENGTH
*/
public Car(String newProposedLicensePlate)
{
setLicensePlate(newProposedLicensePlate);
transmissionType = AUTOMATIC_TRANSMISSION;
odometerInKm = defaultOdometerInKm;
minutesParked = defaultMinutesParked;
}
/**
* @return the license plate of the car can equal null
* but must be between MINIMUM_PLATE_LENGTH and MAXIMUM_PLATE_LENGTH
*/
public String getLicensePlate()
{
return licensePlate;
}
/**
* @return the transmission type MANUAL_TRANSMISSION or AUTOMATIC_TRANSMISSION
*/
public char getTransmissionType()
{
return transmissionType;
}
/**
* @return the odometer in kilometers
*/
public double getOdometerInKm()
{
return odometerInKm;
}
/**
* Recieve the license plate
* Mutator.licensePlate.
* @param proposedLicense String Conforming to ICBC *length* guidlines:
* http://www.icbc.com/vehicle-registration/license-plates/Pages/Personalized-licence-plates.aspx
* May also be null. The null represents a car without a plate
* If validation fails, null will be set.
*/
public void setLicensePlate(String proposedLicense)
{
if(proposedLicense==null){
licensePlate = proposedLicense;
}
else if(proposedLicense.length()>=MINIMUM_PLATE_LENGTH && proposedLicense.length()<=MAXIMUM_PLATE_LENGTH){
licensePlate = proposedLicense;
}
else{
licensePlate = null;
}
}
/**
* @param mOrA recieve the transmission type MANUAL_TRANSMISSION or AUTOMATIC_TRANSMISSION
* if invalid type of transmission is entered then will return "Installation failure: 'mOrA' is not a vaild transmission type"
*/
public void setTransmissionType(char mOrA)
{
if(mOrA==MANUAL_TRANSMISSION){
transmissionType = mOrA;
}
else if(mOrA==AUTOMATIC_TRANSMISSION){
transmissionType = mOrA;
}
else if (mOrA==mOrA){
System.out.println("Installation failure:" + " " + ("'")+(mOrA)+("'") + " " + "is not a valid transmission type.");
}
else{
transmissionType = mOrA;
}
}
/**
* @return the value of the odometer in with the String kilometers
*/
public String readOdometer()
{
return odometerInKm + " " + "kilometers";
}
/**
* @return the false if the minutesParked equals zero; otherwise true
*/
public boolean isParked()
{
if(minutesParked==defaultMinutesParked){
return false;
}
else{
return true;
}
}
/**
* @param duration replaces any existing value in minutesParked with the value from duration
*/
public void park(int duration)
{
if(duration>=defaultMinutesParked){
minutesParked = duration;
}
}
/**
* @param aOdometerInKm recieve the odometer in kilometers
*/
public void setOdometerInKm(double aOdometerInKm)
{
odometerInKm = aOdometerInKm;
}
/**
* @param aMinutesParked recieve the minutes parked in the stall but can not be a negative number
* if invalid number of minutes is entered then the number of minutes will not change.
*/
public void setMinutesParked(int aMinutesParked)
{
if(aMinutesParked>=defaultMinutesParked){
minutesParked = aMinutesParked;
}
else{
return;
}
}
/**
* @return the minutes parked
*/
public int getMinutesParked()
{
return minutesParked;
}
}
这是我的ParkingMeter课程：
/**
* This is a ParkingMeter class for Impark.
*
* @author Tre
* @version 2.0 15 October 2015
*/
public class ParkingMeter
{
private int minutesPaid;
private String methodPaid;
/**
* @param newMinutesPaid the minutes paid for parking meter
*/
public ParkingMeter()
{
}
/**
* @return the minutes paid
*/
public int getMinutesPaid()
{
return minutesPaid;
}
/**
* @return the method paid
*/
public String getMethodPaid()
{
return methodPaid;
}
/**
* @param paidBy the payment method customer will paid by
*/
public void setMethodPaid(String paidBy) /* BONUS for creating method paid */
{
if(methodPaid=="Visa"){
methodPaid = paidBy;
}
else if(methodPaid=="Master Card"){
methodPaid = paidBy;
}
else if(methodPaid=="American Express"){
methodPaid = paidBy;
}
else if(methodPaid=="Cash"){
methodPaid = paidBy;
}
else if(methodPaid=="Debit"){
methodPaid = paidBy;
}
else{
methodPaid = paidBy;
}
}
/**
* @param quantity the added minutes paid must not have a negative number
*/
public void addMinutesPaid(int quantity)
{
if(quantity>=0){
minutesPaid+=quantity;
}
}
}
这是我的ParkingTicket课程：
/**
* This is a ParkingTicket class for Impark.
*
* @author Tre
* @version 1.0
*/
public class ParkingTicket
{
private final String referenceNumber;
private static String carLicensePlate;
private static int carMinutesParked;
private static int meterMinutesPaid;
private static int count = 1000;
private static String PREFIX = "V";
/**
* @param recorededLicense the value of the tick number
*/
private ParkingTicket(String recordedLicense, int newCarMinutesParked, int newMeterPaidMinutes)
{
referenceNumber = (PREFIX+count++);
carMinutesParked = newCarMinutesParked;
meterMinutesPaid = newMeterPaidMinutes;
}
/**
* @param
*/
private ParkingTicket(Car parker, ParkingMeter parkee)
{
this(parker.getLicensePlate(), parker.getMinutesParked(), parkee.getMinutesPaid());
}
/**
* @return referenceNumber the reference number
*/
public String getReferenceNumber()
{
return referenceNumber;
}
/**
* @return carLicensePlate the car's license plate
*/
public String getCarLicensePlate()
{
return carLicensePlate;
}
/**
* @return carMinutesParked the minutes car was parked
*/
public int getCarMinutesParked()
{
return carMinutesParked;
}
/**
* @return meterMinutesPaid the minutes paid on meter
*/
public int getMeterMinutesPaid()
{
return meterMinutesPaid;
}
/**
* @return count the with initial value of 1000
*/
public int getCount()
{
return count;
}
public static ParkingTicket checkParking(int carMinutesParked, int meterMinutesPaid)
{
Car parker = carMinutesParked;
ParkingMeter parkee = parkee;
if(carMinutesParked>meterMinutesPaid){
return new ParkingTicket(parker, parkee);
}
else if(carMinutesParked<=meterMinutesPaid){
return null;
}
return new ParkingTicket(parker, parkee);
}
}
答案 0 :(得分：0)
此要求：
使用Car参数和ParkingMeter参数，决定是否 应该创建ParkingTicket对象。
建议您为checkParking方法提供两个参数，一个属于Car类型，另一个属于ParkingMeter。所以它应该是这样的：
public static ParkingTicket checkParking(Car car, ParkingMeter meter)
此代码：
Car parker = carMinutesParked;
ParkingMeter parkee = parkee;
甚至没有编译
您会看到，只有Car对象包含有关停车时间的信息，您需要对象来创建停车票。 ParkingMeter
反之亦然 - 您从对象中获取值：
int carMinutesParked = car.getMinutesParked();
int meterMinutesPaid = meter.getMinutesPaid();
并使用if从此处继续（或者甚至在if中使用它而不声明临时变量）。
这一个：
你没事。如果票证是值得的，则调用ParkingTicket（parker，parkee），和 返回结果。
现在这个要求：
如果票证不值得，则返回null。
建议该方法将返回null，而不是等于＆＃34; null＆＃34;
因此，根据这些要求，它应该是：
public static ParkingTicket checkParking(Car car, ParkingMeter meter)
{
//sanity check (bonus)
if ((car == null) || (meter == null))
return null;
if(car.getMinutesParked() > meter.getMinutesPaid()){
return new ParkingTicket(car, meter);
}
return null;
}
但请注意，我不知道您是否需要此代码中的任何其他逻辑，并且不建议这应该是您的最终版本，只是解释一般方法。