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public class Library{
private ArrayList<Book> books = new ArrayList<Book>();
public void addBook()
{
Scanner sc = new Scanner(System.in);
System.out.println("Enter title of the book: ");
String title = sc.nextLine();
System.out.println("Enter the author: ");
String author = sc.nextLine();
String bookID = bookID();
Book b = new Book(author,title,bookID,true);
books.add(b);
System.out.println( title + " by "+ author +" added to library.");
System.out.println("Book ID: " + bookID);
}
public void listBooks()
{
for (Book temp : books)
{
if (temp.loanStatus() == true) System.out.print("*");
System.out.println(temp.getTitle() + " by " + temp.getAuthor()+
"ID: " + temp.getID());
}
}
}
Here's my Book class:
public class Book {
private String author;
private String title;
private String ID;
private boolean loanRecord = true;
public Book(String au, String titl, String id, boolean loan)
{
au = author;
titl = title;
loan = loanRecord;
id = ID;
}
public String getTitle()
{
return title;
}
public String getAuthor()
{
return author;
}
public String getID()
{
return ID;
}
public boolean loanStatus()
{
return loanRecord;
}
public void checkoutBook()
{
loanRecord = false;
}
public void returnBook()
{
loanRecord = true;
}
}
For some reason, when I call my listBooks() method to list all of the books added to the books ArrayList, every Book object that I have added comes out as null instead of the desired string instances that I expect.
You swapped your assignments in your constructor.
It should be:
public Book(String au, String titl, String id, boolean loan){
author = au;
title = titl;
loanRecord = loan;
ID = id;
}
As a quick note, you could override the toString method in your Book class and simply do:
for (Book temp : books){
if (temp.loanStatus())
System.out.print("*");
System.out.println(temp);
}
The constructor is wrong:
public Book(String au, String titl, String id, boolean loan)
{ au = author; titl = title; loan = loanRecord; id = ID; }
should be:
public Book(String au, String titl, String id, boolean loan)
{ author = au; title = titl; loanRecord = loan; ID = id; }
Another thing to consider would be to override the default toString() method in the Book class. Then you could print the objects using just:
for(Book b : books)
System.out.println(b);
I would suggest you to refactor your Book class ,
public class Book {
private String author;
private String title;
private String ID; // the name can be changed to id , if you are fine with it
private boolean loanRecord = true;
public Book(String author, String title, String id, boolean loan) {
this.author = author;
this.title = title;
this.ID = id;
this.loanRecord = loan;
}
public String getTitle() {
return title;
}
public String getAuthor() {
return author;
}
public String getID() {
return ID;
}
public boolean loanStatus() {
return loanRecord;
}
public void checkoutBook() {
loanRecord = false;
}
public void returnBook() {
loanRecord = true;
}
}
Related
I have this construct in .Author
package author;
public class Author {
private String name;
private String email;
private char gender;
public Author (String name, String email, char gender) {
this.name = name;
this.email = email;
this.gender = gender;
}
public String getName () {
return name;
}
public char gender () {
return gender;
}
public String getEmail () {
return email;
}
public void SetEmail (String userEmail) {
email = userEmail;
}
public String toString () {
return "Author info: " + " [name: " +name + ", " + " gender: " + gender +", " + " email " + email + "]";
}
}
I have another class named .Book, I want to use the "name" variable from the Author construct inside another construct inside the .Book as shown below:
public class Book {
private String bookName;
private String author;
private double price;
private int qty;
public Book (String bookName, Author name, double price) {
this.bookName = bookName;
// here I'm getting an error saying ";" required
this.author = Author name;
this.price = price;
}
}
I'm getting an error (shown in the second code) so clearly I'm not doing it right and don't know how. Any help?
public class Book {
private String bookName;
private Author author; //it should be Author, not String
private double price;
private int qty;
public Book (String bookName, Author name, double price) {
this.bookName = bookName;
this.author = name; //here was ur mistake
this.price = price;
}
}
Try this code. Assumed, while constructing the book, you do like
Book book = new Book("name", new Author("name", "name#mail", m), 22.0);
So Basically, I'm currently having a problem with my program, where I would like to create an array list of objects and have the values placed by the user, I've yet to go about how to doing that.
In my main class, I've created these attributes.
List<Games> games = new ArrayList<Games>();
List<Company> company = new ArrayList<Company>();
int userchoice;
And in the games.java class I used similar attributes for receiving data.
games.java
public List<Games> getTitles() {
return titles;
}
public void setTitles(List<Games> titles) {
this.titles = titles;
}
I would use games.add(gameTitle); to place values, but it would give me 2 errors.
One of them would tell me that incompatible types: String cannot be converted into Games when I use the games.add(1, gamesTitle);
The next would tell me
method collection.Add(Games) is not applicable, String cannot be converted to Games.
What I'm trying to do is to get the user values from gameID and game Title, into an arrayList that will then send that data to classes as arguments and place them into a database.
This is a Java Persistence API project I'm working on and any help would be appreciated. Thank you
Games.java Class
#Entity (name = "Games")
public class Games implements Serializable {
#Id
private int id;
private String title;
private String genre;
#ManyToOne
#JoinColumn(name="GamesComp")
private Company comp_Name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getGenre() {
return genre;
}
public void setGenre(String genre) {
this.genre = genre;
}
public Company getComp_Name() {
return comp_Name;
}
public void setComp_Name(Company comp_Name) {
this.comp_Name = comp_Name;
}
#Override
public String toString() {
return "Game ID: " + getId() + " Title: " + getTitle() +
" with " + getGenre();
}
Company Class
#Entity
#Table (name="Company")
public class Company implements Serializable {
#Id
private int id;
private String compName;
#OneToMany(cascade = ALL, mappedBy="comp")
private List<Games> titles;
public Company() {
titles = new ArrayList<>();
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getCompName() {
return compName;
}
public void setCompName(String compName) {
this.compName = compName;
}
public void addGameTitles(Games t) {
this.titles.add(t);
t.setComp_Name(this);
}
public List<Games> getTitles() {
return titles;
}
public void setTitles(List<Games> titles) {
this.titles = titles;
}
#Override
public String toString() {
return "Company ID: " + getId() +
", Company Name: " + getCompName();
}
The issue is: you are trying to insert an string object into a List of Games Objects...
replace this List<Games> games = new ArrayList<Games>();
for this:
List<String> games = new ArrayList<String>();
you could of course define the Games Class like
class Games{
...
Games(String gameTitle){
}
and some where in the code add games to the list of games:
games.add(new Games("CallOfDuty"));
imho, the last option is more elegant and reflects a better design model..
but you have the freedom of choice.
I am getting an error saying my constructor Book(String, int) is undefined in my Dictionary class. I check everything else and try to redo my programs still has an error. Any solutions of fixing this issue?
Book Class:
public class Book{
private String author;
private int numPages;
public Book(int code, String title, double price, int quantity, String author, int numPages){
this.author = author;
this.numPages = numPages;
}
//Getters
public String getAuthor(){
return this.author;
}
public int getNumPages(){
return this.numPages;
}
//Setters
public void setAuthor(String author){
this.author = author;
}
public void setNumPages(int numPages){
this.numPages = numPages;
}
//toString
#Override
public String toString(){
String outputBookDes = "";
outputBookDes += "Author: "+ this.author;
outputBookDes += "Number Pages: "+ this.numPages;
return outputBookDes;
}
}
Dictionary Class:
public class Dictionary extends Book{
private String language;
private int numDefinitions;
public Dictionary(String author, int numPages, String language, int numDefinitions){
super(author,numPages);
this.language = language;
this.numDefinitions = numDefinitions;
}
// Getters
public String getLanguage(){
return this.language;
}
public int getNumDefinitions(){
return this.numDefinitions;
}
//Setters
public void setLanguage(String language){
this.language = language;
}
public void setNumDefinitions(int numDefinitons){
this.numDefinitions = numDefinitions;
}
//Ratio method
public double getRatio(){
double ratioTotal = this.numDefinitions / getNumPages();
return ratioTotal;
}
}
As you are calling
super(author,numPages);
in child class Dictionary,
you need to define another constructor in Book class like,
public Book(String author,int numPages) {
this.author = author;
this.numPages = numPages;
}
to get this error solved.
according to your only constructor:
public Book(int code, String title, double price, int quantity, String author, int numPages)
In your main method try:
Book book = new Book(12, "title", 34d, 56, "author", 78);
instead of:
Book book = new Book("34", 56);
I´m quite the noob when it comes to coding. I am about to create a programme where you can add the title (String), author (String), release year (int) and genre (String) of a book from writing it in textfields. These things are supposed to be saved in an arraylist. I can not figure out how to add all of these items to the same slot in the arraylist. Please help as fast as possible.
So you need to create a book class with getters/setters.
public class Book {
public String title;
public String author;
public int year;
public String genre;
}
Then you create a Book
Book book = new Book();
use the setters to set the instance variables (or you can do this when creating book object if you have a constructor with appropriate parameters)
book.setAuthor("R.L.Stein");
once all the fields are set you add the book to an array list.
ArrayList<Book> books = new ArrayList<Book>();
books.add(book);
To print, you should have a toString() method in you book class
public String toString(){
return "Title: "+title+"\nAuthor: "+author+"\nYear: "+year+"\nGenre: "+
genre;
}
Now when you print a book object it will show all its information. It's best to then use a loop to iterate through the list and print each book in books
for(int i=0; i<books.size(); i++){
System.println(books.get(i));
}
Building off of my comment in the original post, here's what your book class should look like:
public class Book {
private String title;
private String author;
private String genre;
private int releaseYear;
public Book(String title, String author, String genre, int releaseYear) {
this.title = title;
this.author = author;
this.genre = genre;
this.releaseYear = releaseYear;
}
public String getTitle() { return this.title; }
public String getAuthor() { return this.author; }
public String getGenre() { return this.genre; }
public int getReleaseYear() { return this.releaseYear; }
}
Now all you need to do is create multiple instances of these classes, and add them into your ArrayList.
Here's a link with some examples of how to use ArrayLists: http://beginnersbook.com/2013/12/how-to-initialize-an-arraylist/
You can do this in two ways.
Create a class containing the title (String), author (String), release year (int) and genre (String) and create a new instance of that class and add it to the array. Here is a javadoc on classes.
(Not recommended, but still works) You can create an array list with a size of 4. The array will be an Object to support the integer. Example: Object[] obj = new Object[]{"title", "author", 2015, "genre"}; You can then take the array and add it to the other array you wanted to add this information to.
If you want to go with choice two and create a class here is an example:
public class Book {
private String title, author, genre;
private int releaseYear;
public Book(String title, String author, int releaseYear, String genre){
this.title = title;
this.author = author;
this.releaseYear = releaseYear;
this.genre = genre;
}
public String getTitle() {
return title;
}
public String getAuthor() {
return author;
}
public String getGenre() {
return genre;
}
public int getReleaseYear() {
return releaseYear;
}
public void setTitle(String title) {
this.title = title;
}
public void setAuthor(String author) {
this.author = author;
}
public void setGenre(String genre) {
this.genre = genre;
}
public void setReleaseYear(int releaseYear) {
this.releaseYear = releaseYear;
}
}
If you wanted to create a new instance of the Book class you would do:
Book book = new Book("title", "author", 2015, "genre");
in this program i need to add 4 books to a library.The code is for my book class but i need to make a method with 4 arguments in another file in my library class that will add the books into a library array.There is a third file for the main where i will print this all out but i just cant figure this out.
Example of book: author-clowney, title-individualism,price-5.50,isbn-978-52-234-43-012
private String author;
private String title;
private double price;
private int isbn;
public book(String a, String t, double p, int i){
author=a;
title=t;
price=checkPrice(p);
isbn=checkIsbn(i);
}
//First and foremost you need to create the book object
public class Book extends Library{
private String author;
private String title;
private double price;
private int isbn;
//Null Constructor-this creates
public book() {
this.author = abcd;
this.title = abcd;
this.price = 0.0;
this.isbn = 0000000;
}
//Now its time for the book with parameters
public book(String a, String t, double p, int i){
author = a;
title = t;
price = p;
isbn = i;
}
//Now it's time to set and get the above values you want
public void setAuthor(String author){
this.author = author;
}
public String getAuthor(){
return this.author;
}
public void setTitle(String title){
this.title = title;
}
public String getTitle(){
return this.title;
}
public void setPrice(double price){
this.price = price;
}
public double getPrice(){
return this.price;
}
public void setIsbn(int isbn){
this.isbn = isbn;
}
public double getIsbn(){
return this.isbn;
}
//Now you are going to want to toString(), that way you can display the books in the library
public String toString() {
//Im assuming you have learned that Library is your super class and has a toString() as well
return(super.toString()+ "Book Author: " + this.author + "Book Title: " + this.title + "Book Price: " + this.price + "Book ISBN: " + this.isbn);
}
}
//Now simply call this method within your main method to display books in Output!!
//Hope this helps, if you have further questions please leave below!!