Date オブジェクトへの参照を比較する必要があるプログラムに問題があります。シナリオは車両ショールームで、車両は配列リストに格納されています。
私は車両クラスを持っています
import java.text.DecimalFormat;
import java.util.*;
import java.util.Date;
public class Vehicle {
private String manufacturer;
private String model;
//private String customerNameSold = null;
private String vehicleID_VIN;
private String dateManufacture;
private String dateSold;
private boolean beenSold;
private char taxBand_A_M;
private double vehicleCost;
private String emissions;
private Customer customerNameSold;
private Date dom;
//private String manuDate;
private Date saleDate;
//Constructor 7
public Vehicle (String manu, String mod, String vin, String dateManu, char tax, double cost){
manufacturer = manu;
model = mod;
vehicleID_VIN = vin;
dateManufacture = dateManu;
//Add String to Date
dom = new Date(dateManu);
taxBand_A_M = tax;
vehicleCost = cost;
dateSold = null;
customerNameSold = null;
beenSold = false;
}
public String toString() {
DecimalFormat df = new DecimalFormat("#.00");
//method calls - do they need this. then method call?
String s = "\nManufacturer: " + getManu()
+ " \nModel: " + getModel()
+ " \nVIN: " + getVin()
+ " \nDate of Manufacture: " + getManuDate()
+ " \nDate of Manufacture (String to Date): " + getManuDate2()
+ " \nAge of Vehicle: " + getAgeOfVehicle() + " (in WEEKS)"
+ " \nTax Band: " + getTax()
+ " \nEmissions: " + cO2()
+ " \nCost: £" + df.format(getCost())
+ " \nHas Vehicle Been Sold: " + getBeenSold()
+ " \nCustomer: " + getCust()
+ " \nDate Sold: " + getDateSold()
+ " \nDate Sold (String to Date): " + getDateSold2();
return s;
}
public String getManu() {
return manufacturer;
}
public String getModel() {
return model;
}
//// public String getCust() {
////
//// return customerNameSold;
//// }
public Customer getCust() {
return customerNameSold;
}
public String getVin() {
return vehicleID_VIN;
}
public String getManuDate(){
return dateManufacture;
}
public Date getManuDate2() {
return dom;
}
public String getDateSold(){
return dateSold;
}
public Date getDateSold2() {
return saleDate;
}
//CONVENTION SUGGESTS SHOULD BE 'isSold()'
public boolean getBeenSold() {
return beenSold;
}
public char getTax() {
return taxBand_A_M;
}
public double getCost() {
//how to format to 2 decimal places?
return vehicleCost;
}
public void buyVehicle(String sale, Customer cust) {
customerNameSold = cust;
//Add String to Date
saleDate = new Date(sale);
dateSold = sale;
beenSold = true;
}
public String cO2() {
switch (taxBand_A_M) {
case 'A':
emissions = "0-100";
break;
case 'B':
emissions = "101-110";
break;
case 'C':
emissions = "111-120";
break;
case 'D':
emissions = "121-130";
break;
case 'E':
emissions = "131-140";
break;
case 'F':
emissions = "141-150";
break;
case 'G':
emissions = "151-160";
break;
default:
emissions = null;
break;
}
return emissions;
}
public int getAgeOfVehicle() {
Date now = new Date();
long diff = now.getTime() - dom.getTime();
long age = (diff / (1000L * 60 * 60 * 24 * 7));
return (int) age;
}
}
ショールームクラス
import java.util.*;
public class Showroom {
private String showroomName;
private ArrayList<Vehicle> theVehicles;
private Vehicle currVeh = null;
private ArrayList<Vehicle> recentlySold;
private Date dateSold;
private long diff;
private long age;
//Constructor Method - Takes the name of the Showroom Object & Creates the array list of vehicles
public Showroom(String name) {
showroomName = name;
theVehicles = new ArrayList<Vehicle>();
}
public String getName() {
return showroomName;
}
public void setName(String name) {
//this.showroomName if passed in parameter was named showroomName also
showroomName = name;
}
public boolean addVehicle(Vehicle newVehicle) {
theVehicles.add(newVehicle);
currVeh = newVehicle;
return true;
}
public boolean addVehicleAfterCurrent(Vehicle newVehicle) {
theVehicles.add(theVehicles.indexOf(currVeh) + 1, newVehicle);
currVeh = newVehicle;
return true;
}
public Vehicle findVehicle(String vehicleVIN) {
for (Vehicle v : theVehicles) {
if (v.getVin().equalsIgnoreCase(vehicleVIN)) {
System.out.println("Vehicle Found:\n"
+ v.getManu() + "\n"
+ v.getModel() + "\n"
+ v.getVin() + "\n"
+ theVehicles.indexOf(v) + "\n");
return v;
//OR CALL THE toString() METHOD - v.toString()
}
}
System.out.println("Sorry - The Vehicle was not found in the Showroom!\n"
+ theVehicles.indexOf(vehicleVIN) + "\n");
return null;
}
public Vehicle setCurrentVehicle(Vehicle cv) {
currVeh = cv;
return currVeh;
}
public Vehicle getCurrentVehicle() {
System.out.println("\nCurrentVehicle: " + currVeh);
return currVeh;
}
public Vehicle nextVehicle() {
int index = theVehicles.indexOf(currVeh);
if (index < 0 || index + 1 == theVehicles.size()) {
System.out.println("\nEnd of the list");
return null;
}
Vehicle v = theVehicles.get(index + 1);
setCurrentVehicle(v);
System.out.println("\nThe Former Next Vehicle & Now Current Vehicle: " + v);
return currVeh;
}
public Vehicle previousVehicle() {
int index = theVehicles.indexOf(currVeh);
if (index <= 0) {
System.out.println("\nNegative Index -1 Before Start of List");
return null;
}
Vehicle v = theVehicles.get(index - 1);
setCurrentVehicle(v);
System.out.println("\nThe Former Previous Vehicle & Now Current Vehicle: " + v);
return currVeh;
}
public void outputArray() {
for (Vehicle nextVehicle : theVehicles) {
System.out.println(nextVehicle.getModel() + "\n" + theVehicles.indexOf(nextVehicle));
}
}
public void outputShowroomDetails() {
System.out.println("\nSHOWROOM NAME: " + showroomName);
//output each vehicle in turn
System.out.println("THE VEHICLES IN THE SHOWROOM:");
if (theVehicles.isEmpty()) {
System.out.println("\n*** There are no Vehicles in the Showroom! ***");
} else {
for (Vehicle nextVehicle : theVehicles) {
System.out.println(nextVehicle.toString() + "\n" + theVehicles.indexOf(nextVehicle));
}
}
}
public Vehicle setCurrentVehicleByVIN(String vin) {
System.out.println("\n*** ATTEMPTING TO SET CURRENT VEHICLE BY VIN:\n"
+ vin);
Vehicle v = findVehicle(vin);
if (v != null) {
System.out.println("\nTHE CURRENT VEHICLE: " + "\nARRAY LIST INDEX: " + theVehicles.indexOf(v)
+ v.toString());
}
currVeh = v;
return currVeh;
}
public boolean deleteVehicle(String vin) {
System.out.println("\nATTEMPTING TO DELETE VEHICLE:\n"
+ "VEHICLE VIN to DELETE: " + vin);
Vehicle v = findVehicle(vin);
if (v != null) {
theVehicles.remove(v);
System.out.println("VEHICLE *** " + vin + " *** REMOVED!");
return true;
}
return false;
}
//Method not working - null pointer 'long diff' line
public ArrayList<Vehicle> getVehiclesSoldRecently() {
recentlySold = new ArrayList<Vehicle>();
//Each vehicle has a sale date
//Determine the difference between sale date & todays date
//If the difference is greater than 14 days (2 weeks) it won't be added to the array
//If the difference is less than or equal to 14 days (2 weeks), then they will be added to the array
if (theVehicles.isEmpty()) {
System.out.println("\n*** The Showroom is Empty!***");
} else
{
for (Vehicle v : theVehicles) {
Date now = new Date();
dateSold = v.getDateSold2();
long diff = now.getTime() - v.getDateSold2().getTime();
long age = (diff / (1000L * 60 * 60 * 24 * 7));
if (age <= 2) {
recentlySold.add(v);
System.out.println("\nVEHICLES RECENTLY SOLD: " + v.toString());
}
}
return recentlySold;
}
}
&顧客クラス
public class Customer {
private String custName = null;
private String custPhone = null;
private String custEmail = null;
public Customer() {
}
public Customer(String name) {
custName = name;
custPhone = "n/a";
custEmail = "n/a";
}
public Customer(String name, String phone) {
custName = name;
custPhone = phone;
custEmail = "n/a";
}
//***CAN'T HAVE A CONSTRUCTOR DETAILING NAME & EMAIL ONLY
//AS A (String, String) CONSTRUCTOR ALREADY DEFINED
public Customer(String name, String phone, String email) {
custName = name;
custPhone = phone;
custEmail = email;
}
//***AUTO GENERATED GETTERS & SETTERS - this.*
public String getCustName() {
return custName;
}
public void setCustName(String custName) {
this.custName = custName;
}
public String getCustPhone() {
return custPhone;
}
public void setCustPhone(String custPhone) {
this.custPhone = custPhone;
}
public String getCustEmail() {
return custEmail;
}
public void setCustEmail(String custEmail) {
this.custEmail = custEmail;
}
//***AUTO GENERATED TOSTRING METHOD (THOUGH EDITED FOR FORMAT)
@Override
public String toString() {
String cust = "\n*** CUSTOMER ***"
+ "\nName: " + getCustName()
+ "\nPhone: " + getCustPhone()
+ "\nEmail: " + getCustEmail();
//System.out.println(cust);
return cust;
}
}
ショールームドライバーは
public class ShowroomDriver {
public static void main(String args[]) {
Showroom showDrive = new Showroom("ShowroomDriver Showroom");
System.out.println("\n*** OUTPUT SHOWROOM DETAILS ***");
showDrive.outputShowroomDetails();
System.out.println("\n*** CREATE / ADD 4 VEHICLES ***");
Vehicle sdv1 = new Vehicle("Audi", "R8 Spider", "FAVE 101", "MAR-04-2011", 'E', 45000);
//Vehicle sdv1 = new Vehicle("Audi", "R8 Spider", "FAVE 101", 03 / 04 / 2011, 'E', 45000);
System.out.println("\nTesting toString: " + sdv1.toString());
Vehicle sdv2 = new Vehicle("Tesla", "Model S", "ELEC TRIC", "JAN-01-2013", 'A', 55000);
//Vehicle sdv2 = new Vehicle("Tesla", "Model S", "ELEC TRIC", 01 / 01 / 2013, 'A', 55000);
System.out.println("\nTesting to String: " + sdv2.toString());
Vehicle sdv3 = new Vehicle("Ford", "Cortina", "1212 NUM", "JUN-06-2006", 'D', 55000);
//Vehicle sdv3 = new Vehicle("Ford", "Cortina", "1212 NUM", 06 / 06 / 2006, 'D', 55000);
System.out.println("\nTesting to String: " + sdv3.toString());
Vehicle sdv4 = new Vehicle("VW", "Golf MK 1", "DUB DUB", "NOV-11-1971", 'E', 25000);
//Vehicle sdv4 = new Vehicle("VW", "Golf MK 1", "DUB DUB", 11/11/1971, 'E', 25000);
System.out.println("\nTesting to String: " + sdv4.toString());
showDrive.addVehicle(sdv1);
showDrive.addVehicle(sdv2);
showDrive.addVehicle(sdv3);
showDrive.addVehicle(sdv4);
System.out.println("\n*** OUTPUT SHOWROOM DETAILS ***");
showDrive.outputShowroomDetails();
System.out.println("\n*** BUY 2 VEHICLES ***");
Customer cust1 = new Customer("Andrew Antivan", "01785 111 111");
Customer cust2 = new Customer("Belinda Belle", "01782 222 222", "belbel@gmail.com");
sdv1.buyVehicle("JUL-07-2013", cust1);
sdv2.buyVehicle("MAR-01-2013", cust2);
showDrive.outputShowroomDetails();
System.out.println("\n***CREATE 4 VEHICLES ***");
Vehicle purV1 = new Vehicle("Ford", "Fiesta", "NAT NAT", "MAR-09-2006", 'E', 5000);
Vehicle purV2 = new Vehicle("Vauxhall", "Corsa", "LEE 123", "JUL-07-2011", 'D', 5500);
Vehicle purV3 = new Vehicle("Toyota", "Aygo", "JOHN 32A", "FEB-02-2010", 'E', 2000);
Vehicle purV4 = new Vehicle("Marvel", "Bat Mobile", "KA BOOM", "MAR-11-2008", 'C', 3000);
System.out.println("\n*** SELL 2 of 4 VEHICLES ***");
System.out.println("\n*** ADD THE 4 NEW VEHICLES TO SHOWROOM ***");
showDrive.addVehicle(purV1);
showDrive.addVehicle(purV2);
showDrive.addVehicle(purV3);
showDrive.addVehicle(purV4);
purV1.buyVehicle("DEC-12-2012", cust1);
purV2.buyVehicle("DEC-12-2012", cust1);
purV3.buyVehicle("OCT-18-2013", cust2);
purV4.buyVehicle("OCT-19-2013", cust2);
showDrive.outputShowroomDetails();
showDrive.getVehiclesSoldRecently();
}
}
プログラムは段階的に変更されます。元々、製造および販売の日付は文字列オブジェクトとして (ハードコードされて) 渡されていましたが、現在は日付オブジェクトとして追加する必要があります。
私が抱えている問題は、getVehiclesSoldRecently() メソッドを呼び出そうとしたときにのみ発生しました。そのメソッドの「diff...」行が原因で問題が発生していることを示唆するヌル ポインター例外の警告が表示されます。
受信したエラー:
スレッド「メイン」での例外 java.lang.NullPointerException
Showroom.getVehiclesSoldRecently (Showroom.java:197) で
diff=now.getTime()-v.getDateSold2().getTime();
ShowroomDriver.main(ShowroomDriver.java:93) で
showDrive.getVehiclesSoldRecently();
getDates を除くすべてのメソッドのメソッド シグネチャは同じままにする必要があります。つまり、String パラメータを渡して Date オブジェクトに変換する必要がありました。
私が間違っている場所を示すための助けをいただければ幸いです。
ありがとう。