I have an assignment and my superclass default values always override the values I pass in the Test main method. In the debugger, i see the passing of the productNumber(1234) and productTitle("Daughter"), but then it's overridden with the default values. Any thoughts, i keep making minor changes, checking for changes, still the same results.
Product Superclass
public abstract class Product {
private int productNumber;
private String productTitle;
//Two constructors required
public Product(){
productNumber = 0;
productTitle = "";
}
public Product(int productNumber, String productTitle) {
this.productNumber = productNumber;
this.productTitle = productTitle;
}
public void setProductNumber(int productNumber) {
this.productNumber = productNumber;
}
public int getProductNumber() {
return productNumber;
}
public void setProductTitle(String productTitle) {
this.productTitle = productTitle;
}
public String getProductTitle() {
return productTitle;
}
//Override toString() required
#Override
public String toString() {
return productNumber + " " + productTitle;
}
// Required Product class declares abstract method with this signature: public String getDisplayText()
public abstract String getDisplayText();
//Override equals() required
#Override
public boolean equals(Object object) {
if (object instanceof Product) {
Product product2 = (Product) object;
if (productNumber == (product2.getProductNumber()) &&
productTitle.equals(product2.getProductTitle())){
return true;
}
}
return false;
}
}
Music Subclass extends Product Superclass
public class Music extends Product {
private String artist;
private String style;
private String medium;
public Music() {
super();
artist = "";
style = "";
medium = "";
}
public Music(int productNumber, String productTitle, String artist, String style, String medium) {
super();
this.artist = artist;
this.style = style;
this.medium = medium;
}
public String getArtist() {
return artist;
}
public void setArtist(String artist) {
this.artist = artist;
}
public String getStyle() {
return style;
}
public void setStyle(String style) {
this.style = style;
}
public String getMedium() {
return medium;
}
public void setMedium(String medium) {
this.medium = medium;
}
#Override
public String getDisplayText() {
return super.toString() + " by " + artist + " " + style + " " + medium;
}
#Override
public boolean equals(Object object){
if (object instanceof Music){
Music m = (Music) object;
if (artist.equals(m.getArtist()) &&
style.equals(m.getStyle()) &&
medium.equals(m.getMedium())){
return true;
}
}
return false;
}
}
Print String
public class Test {
public static void main(String[] args) {
// Expected result: 1234 Daughter by Pearljam Alternative online
Music music1 = new Music(1234,"Daughter", "Pearljam","Alternative","online");
System.out.println(music1.getDisplayText());
}
}
you are not passing values from subclass to your parentclass
instead of super() you need to do below -
super(productNumber,productTitle);
update needed in your code :-
public Music(int productNumber, String productTitle, String artist, String style, String medium) {
super(productNumber,productTitle);
this.artist = artist;
this.style = style;
this.medium = medium;
}
You need to pass productNumber and productTitle in the super(..., ...) call inside the Music constructor up to the parent class.
You need to invoke
super(productNumber, productTitle)
inside the Music constructor to pass the parameters to its parent.
Related
I am trying to save an enum 'Status' into a custom class that implements parcelable. I have found online how I can save Strings, ints or enums in one class that implements parcelable, but not how I can save these three things all at once. I am sorry if the solution is obvious, but I just can't figure it out.
Here is what my enum looks like:
public enum Status {
INITIALIZED, UPDATED, DELETED
}
And this is what I have so far:
public class Recipe implements Parcelable{
private String id;//this should be an int, same problem
private String recipeName;
private String recipePreperation;
private Status status;
private final static int MAX_PREVIEW = 50;
public Recipe(int parId, String parRecipeName, String parRecipePreperation) {
this.id = "" + parId;
this.recipeName = parRecipeName;
this.recipePreperation = parRecipePreperation;
this.status = Status.INITIALIZED;
}
public Recipe(Parcel in){
String[] data = new String[4];
in.readStringArray(data);
this.id = data [0];
this.recipeName = data[1];
this.recipePreperation = data[2];
this.status = data[3];//what I intend to do, I know this is wrong
}
public int GetId() {
return Integer.parseInt(id);
}
public String GetRecipeName() {
return this.recipeName;
}
public void SetRecipeName(String parRecipeName) {
this.recipeName = parRecipeName;
}
public String GetRecipePreperation() {
return this.recipePreperation;
}
public void SetRecipePreperation(String parRecipePreperation) {
this.recipePreperation = parRecipePreperation;
}
public Status GetStatus() {
return this.status;
}
public void SetStatus(Status parStatus) {
this.status = parStatus;
}
public String toString() {
String recipe = this.recipeName + "\n" + this.recipePreperation;
String returnString;
int maxLength = MAX_PREVIEW;
if (recipe.length() > maxLength) {
returnString = recipe.substring(0, maxLength - 3) + "...";
} else {
returnString = recipe;
}
return returnString;
}
#Override
public int describeContents() {
return 0;
}
#Override
public void writeToParcel(Parcel dest, int arg1) {
dest.writeStringArray(new String [] {
this.id,
this.recipeName,
this.recipePreperation,
this.status//what I intend to do, I know this is wrong
});
}
public static final Parcelable.Creator CREATOR = new Parcelable.Creator() {
public Recipe createFromParcel(Parcel in) {
return new Recipe(in);
}
public Recipe[] newArray(int size) {
return new Recipe[size];
}
};
}
How do I save an int, an array of strings and an enum into a class that implements the parcelable, so it can writeToParcel()?
There's no need to read and write to/from string array. Just write each string and finally the status as Serializable. This is how I fix it.
public Recipe(Parcel in){
this.id = in.readString();
this.recipeName = in.readString();
this.recipePreperation = in.readString();
this.status = (Status) in.readSerializable();
}
public void writeToParcel(Parcel dest, int arg1) {
dest.writeString(this.id);
dest.writeString(this.recipeName);
dest.writeString(this.recipePreperation);
dest.writeSerializable(this.status);
}
I am trying to print title from my member class using array in my library class
public class Book gives me this error :
http://screencast.com/t/tqpJp2BF8sH
{
// instance variables - replace the example below with your own
private int x;
private Integer bookid;
private String author;
private String title;
private String ficornonfic;
/**
* Constructor for objects of class Book
*/
public Book(Integer bookID, String Author, String Title, String FictionORnonfiction )
{
bookid = bookID;
author = Author;
title = Title ;
ficornonfic = FictionORnonfiction;
x = 0;
}
public String PrintListOfBooks()
{
return title;
}
public String toString() {
return "Title:" + title + " BookId: " + bookid + " Author: " + author + ".";
}
public int getTitle() {
return this.title;
}
}
---------------------------------------------------------
this is my library class
import java.util.ArrayList;
public class Library
{
private ArrayList<Member>listOfMembers;
public Library()
{
listOfMembers = new ArrayList<Member>();
listOfBooks = new ArrayList<Book>();
}
public void storeMember(Member Member)
{
listOfMembers.add(Member);
}
public int numberOfMembers()
{
return listOfMembers.size();
}
public void listMembers()
{
for (int item=0; item<listOfMembers.size(); item++ ) {
Member m = listOfMembers.get (item);
System.out.println(m.GetWholeName());
}
}
public Member findMember(int id) {
for(Member member : listOfMembers) {
if (member.getId() == id) {
return member;
}
}
return null;
}
private ArrayList<Book>listOfBooks;
public void storeBook(Book Book)
{
listOfBooks.add(Book);
}
public int numberOfBooks()
{
return listOfBooks.size();
}
public void listBooks()
{
for (int item=0; item<listOfBooks.size(); item++ ) {
Book b = listOfBooks.get (item);
System.out.println(b.PrintListOfBooks());
}
}
public Book findBook(string title) {
for(Book book : listOfBooks) {
if (book.getId() == id) {
return book;
}
}
return null;
}
}
I am trying to print title from my member class using array in my library class
public class Book gives me this error :
http://screencast.com/t/tqpJp2BF8sH
The title is a String, not an int. You can change the method signature to match the field type:
public String getTitle() {
return this.title;
}
First, as others have noted your title is a String not an int. So change the return type of getTitle() (or remove it altogether). Because it appears like you've correctly overridden toString() in Book to get all the information, and you could iterate the contents of your List with a for-each loop. Something like,
for (Book b : listOfBooks) {
System.out.println(b);
}
which is equivalent to
for (int i = 0; i < listOfBooks.size(); i++) {
Book b = listOfBooks.get(i);
System.out.println(b.toString());
}
Finally in Java, by convention, method names start with a lower case letter.
You are essentially telling the program to return an Integer when the value you wish to return is a String.
If you change int to String, the error will go away.
public String getTitle() {
return this.title;
}
I have 2 classes that extend for each other. I have a mutator method that is calling to the class Address.Java to get the city and state from the class. However the Bank.java class is giving me problems. the specific method giving me problems is
public void setBankAddress(String aCity, String aState)(code is below) I dont know if this makes sense
{
}
Bank.Java
public class Bank
{
private String bankName;
private int bankID;
private Address bankAddress;
public Bank()
{
bankName = "?";
bankID = 0;
bankAddress = new Address();
}
public String getBankName()
{
return bankName;
}
public int getBankID()
{
return bankID;
}
public Address getBankAddress()
{
return bankAddress;
}
public void setBankName(String aBankName)
{
bankName = aBankName;
}
public void setBankID(int aBankID)
{
bankID = aBankID;
}
public void setBankAddress(String aCity, String aState)
{
}
public String toString()
{
return "\nBank name:\t\t" + bankName + "\nBank ID:\t\t" + bankID + "\nBank Address:\t\t" + bankAddress + "\n\n";
}
}
Address. Java
public class Address
{
private String city;
private String state;
public Address()
{
city = "?";
state = "?";
}
public String getCity()
{
return city;
}
public String getState()
{
return state;
}
public void setCity(String aCity)
{
city = aCity;
}
public void setState(String aState)
{
state = aState;
}
public String toString()
{
return city + "," + state;
}
}
Do you just not know how to call methods on objects?
public void setBankAddress(String aCity, String aState)
{
bankAddress.setCity(aCity);
bankAddress.setState(aState);
}
bankAddress is already initialized in the constructor so you can safely call these methods.
However, it's usually good practice to do that outside such methods and pass the whole object itself
Address someAddress = new Address();
someAddress.setCity(aCity);
someAddress.setState(aState);
Bank bank = new Bank();
bank.setBankAddress(someAddress);
...
public void setBankAddress(Address aBankAddress) {
bankAddress = aBankAddress;
}
public class ParkedCar {
private String make;
private String model;
private String color;
private String licenseNum;
public ParkedCar(String make, String model, String color, String licenseNum) {
this.make = make;
this.model = model;
this.color = color;
this.licenseNum = licenseNum;
}
public void setMake(String ma) {
make = ma;
}
public void setModel(String mo) {
model = mo;
}
public void setColor(String c) {
color = c;
}
public void setLicenseNum(String ln) {
licenseNum = ln;
}
public String getMake() {
return make;
}
public String getModel() {
return model;
}
public String getColor() {
return color;
}
public String getLicenseNum() {
return licenseNum;
}
}
public class ParkingMeter {
private ParkedCar parkedcar;
private int timePurchased;
private int timeParked;
public ParkingMeter(ParkedCar parkedcar, int timePurchased, int timeParked) {
this.parkedcar = parkedcar;
this.timePurchased = timePurchased;
this.timeParked = timeParked;
}
/*public ParkingMeter (ParkedCar parkedcar) {
this.parkedcar = null;
}*/
public void setTimePurchased(int timePurchased) {
this.timePurchased = timePurchased;
}
public int getTimePurchased() {
return timePurchased;
}
public void setTimeParked(int timeParked) {
this.timeParked = timeParked;
}
public int getTimeParked() {
return timeParked;
}
public int TimeExpired() {
if (timeParked > timePurchased)
return timeParked - timePurchased;
else
return 0;
}
public String toString() {
return "Make: " + parkedcar.getMake() + "\nModel: " + parkedcar.getModel() + "\nColor: " + parkedcar.getColor() + "\nLicense Number: " + parkedcar.getLicenseNum();
}
}
public class ParkingTicket {
private ParkingMeter parkingmeter;
public ParkingTicket(ParkingMeter parkingmeter) {
this.parkingmeter = parkingmeter;
}
public int TicketCost() {
if (parkingmeter.getTimeParked() > parkingmeter.getTimePurchased()) {
if (parkingmeter.getTimeParked() <= 60)
return 25;
else
return 25 + (10*(parkingmeter.TimeExpired())/60);
}
else
return 0;
}
}
public class PoliceOfficer {
private String OfficerName;
private int OfficerNum;
private ParkingMeter pm;
private ParkingTicket pt;
public PoliceOfficer(ParkingTicket pt, String OfficerName, int OfficerNum) {
this.OfficerName = OfficerName;
this.OfficerNum = OfficerNum;
}
public void setOfficerName(String OfficerName) {
this.OfficerName = OfficerName;
}
public void setOfficerNum(int OfficerNum) {
this.OfficerNum = OfficerNum;
}
public String getOfficerName() {
return OfficerName;
}
public int getOfficerNum() {
return OfficerNum;
}
public boolean isExpired() {
if (pm.getTimeParked() > pm.getTimePurchased())
return true;
else
return false;
}
public String toString() {
return "Officer Name: " + OfficerName + "\nOfficer Number: " + OfficerNum + "\n" + "\nFine: " + pt.TicketCost();
}
}
public class ParkingTicketDemo {
public static void main(String[] args) {
ParkedCar pc = new ParkedCar("Toyota", "Camry", "Blue", "BXZ 152");
System.out.println(pc);
ParkingMeter pm = new ParkingMeter(pc, 60, 120);
ParkingTicket pt = new ParkingTicket(pm);
PoliceOfficer po = new PoliceOfficer(pt, "Roger", 337);
System.out.println(po);
}
}
I have been trying to create a program to create and issue a parking ticket and have run into the problem where it compiles, but when it runs it gives out the error message Exception in thread "main" java.lang.NullPointerException. I am a fairly new programmer and this is the first time I have encountered the problem so I have yet fully understand it and cannot seem to fix it. i have tried reading other things online, but just do not understand I would love a simple explaination to my problem.
The NPE happens because of these two lines:
PoliceOfficer po = new PoliceOfficer(pt, "Roger", 337);
System.out.println(po);
In your constructor for PoliceOfficer, you don't do anything with the ParkingTicket instance pt.
public PoliceOfficer(ParkingTicket pt /* not set anywhere */, String OfficerName, int OfficerNum) {
this.OfficerName = OfficerName;
this.OfficerNum = OfficerNum;
}
The fields ParkingMeter pm and ParkingTicket pt remain null since you haven't initialized them.
Then you try to print the object: System.out.println(po); What this does is call toString() on po, it is equivalent to this:
System.out.println(po.toString());
Now because your toString()
public String toString() {
return "Officer Name: " + OfficerName + "\nOfficer Number: " + OfficerNum + "\n" + "\nFine: " + pt.TicketCost();
}
uses the pt, it creates a NullPointerException, since pt is null.
Since you are already passing a ParkingTicket instance into the constructor for PoliceOfficer, use that instance to assign its member variable pt.
I get such a JSON from the server and want to parse it to my objects:
"product":{
"product_type":"assignment",
"id":717,
"product_profile":{
"title":"new Order from java",
"info":"Some special info",
"dtl_expl":true,
"special_info":""
}
}
Depend on "product_type" value I get different value of "product_profile" from server. The "product_profile" can be one of three types. I created class presentation for each of them. But question is that how organize correct parsing of JSON object to my Product class due to OOP principles? Should I create interface and implement it in each of my three classes, or I should create one parent class and extend it in my three classes to make it work right?
My classes structure. First of all Product class , object of which I should get as a result from json:
public class Product {
ProductAssignment prodAss;
ProductWriting prodWr;
ProductType returnState;
#SerializedName("id")
int id;
#SerializedName("product_type")
String product_type;
#SerializedName("product_profile")
ProductType product_profile;
public Product()
{}
public Product(int id, String product_type, ProductType product_profile)
{
this.id = id;
this.product_type = product_type;
this.product_profile = product_profile.returnObject(product_type);
}
public int getProductId()
{
return this.id;
}
public String getProductType()
{
return this.product_type;
}
public ProductType getProduct()
{
return product_profile.returnObject(product_type);
}
public void setProductId(int id)
{
this.id = id;
}
public void setProductTitle(String product_type)
{
this.product_type = product_type;
}
public void setProduct(ProductType product_profile)
{
this.product_profile = product_profile;
}
#Override
public String toString() {
return "id=" + id + " " + "title=" + product_type
+ " " + "profile=" + product_profile + "}";
}
}
Now parent class ProductType for two subclasses:
public class ProductType extends ProductType{
String product;
static ProductType productType;
static ProductAssignment productAssignment;
static ProductWriting productWriting;
IProductType component;
private ProductType returnState;
ProductAssignment prodAss;
ProductWriting prodWr;
public ProductType()
{
}
public ProductType(IProductType c)
{
component = c;
}
// implemented method of interface
#Override
public ProductType returnObject(String product_type)
{
System.out.println("ProductType");
if (product_type.equals("assignment"))
returnState = prodAss.returnObject(product_type);
else if (product_type.equals("writing"))
returnState = prodWr.returnObject(product_type);
System.out.println(returnState.getClass().getName());
return returnState;
}
}
One of the subclasses:
public class ProductWriting extends ProductType{
#SerializedName("id")
int id;
#SerializedName("title")
String title;
#SerializedName("pages_number")
int pages_number;
#SerializedName("number_of_references")
String number_of_references;
#SerializedName("dtl_expl")
boolean dtl_expl;
#SerializedName("info")
String info;
public ProductWriting()
{}
public ProductWriting(String title, String info, boolean dtl_expl,
int pages_number ,
int id,String number_of_references)
{
this.title = title;
this.info = info ;
this.dtl_expl = dtl_expl;
this.id = id;
this.pages_number = pages_number;
this.number_of_references = number_of_references;
}
public ProductWriting(IProductType c){
super(c);
}
// getters and setters
#Override
public ProductType returnObject(String res) {
System.out.println("Writing");
super.returnObject(res);
return new ProductWriting();
}
}
Another one :
public class ProductAssignment extends ProductType{
ProductAssignment thisObj;
#SerializedName("title")
String title;
#SerializedName("info")
String info;
#SerializedName("dtl_expl")
boolean dtl_expl;
#SerializedName("special_info")
String special_info;
#SerializedName("shoot_exclusive_video")
boolean shoot_exclusive_video;
#SerializedName("shoot_common_video")
boolean shoot_common_video;
public ProductAssignment()
{}
public ProductAssignment(String title, String info, boolean dtl_expl, String special_info,
boolean shoot_common_video, boolean shoot_exclusive_video)
{
this.title = title;
this.info = info ;
this.dtl_expl = dtl_expl;
this.special_info = special_info;
this.shoot_common_video = shoot_common_video;
this.shoot_exclusive_video =shoot_exclusive_video;
}
// getters and setters
#Override
public ProductType returnObject(String res) {
System.out.println("Assignment");
super.returnObject(res);
return new ProductAssignment();
}
#Override
public String toString()
{
return "title=" + title + "info " + "=" + info
+ " " + "profile=" + dtl_expl + "}";
}
}
Interface for binding my classes:
public interface IProductType
{
ProductType returnObject(String parse);
}
I tried to implement in this way, but it doesn't work for now with it.