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JavaFX Combobox show attribute of element

I am currently working on a game with Java and JavaFX. I am using a JavaFX ComboBox.
The following example should explain my problem.
Let's say I have a class "Animal" with the attributes "name", "age" and "color".
First file:
public class Animal {
private String name;
private int age;
private String color;
public Animal(String name, int age, String color) {
this.name = name;
this.age = age;
this.color = color;
}
}
Now I want to create a ComboBox with each animal I create.
Second file:
ComboBox<Animal> comboBoxAnimal = new ComboBox();
ObservableList<Animal> comboBoxItems = FXCollections.observableArrayList();
Animal dog = new Animal("Liam", 2, "Brown");
Animal cat = new Animal("Emily", 5, "Gray");
Animal bird = new Animal("Kian", 3, "Green");
comboBoxItems.addAll(dog, cat, bird);
comboBoxAnimal.setItems(comboBoxItems);
Currently I get only "Animal#xxxxxxxx" which is understandable because I have a ComboBox of Animals but want only the names (Strings) to be presented.
Just simply creating a ComboBox<String> won't solve the problem as I need a Combobox<Animal>.
How can I get a Combobox<Animal> but as elements show only the names of each Animal?
Thanks for your feedback :)

Two options:
Use a cell factory.
Use a string converter.
The cell factory and string converter examples used in this answer produce the identical output:
Cell Factory Implementation
Use a cell factory, like in this answer:
How can I Populate a ListView in JavaFX using Custom Objects?
The linked answer is for a ListView, but the ComboBox is similar, as is a TableView or other virtualized controls that rely on cell factories for display.
To configure cells for the ComboBox drop-down list and button, make calls to both setCellFactory and setButtonCell.
This is the most flexible solution and allows for customization beyond just strings of text. Graphic nodes can be created to completely customize the visual representation of each combo box cell.
Example Code
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.ComboBox;
import javafx.scene.control.ListCell;
import javafx.stage.Stage;
public class AnimalComboApp extends Application {
public record Animal(String name, int age, String color) {}
public static class AnimalCell extends ListCell<Animal> {
#Override
public void updateItem(Animal animal, boolean empty) {
super.updateItem(animal, empty);
if (animal == null || empty) {
setText(null);
} else {
setText(animal.name());
}
}
}
#Override
public void start(Stage stage) throws Exception {
ComboBox<Animal> comboBox = new ComboBox<>();
comboBox.getItems().setAll(
new Animal("Liam", 2, "Brown"),
new Animal("Emily", 5, "Gray"),
new Animal("Kian", 3, "Green")
);
comboBox.setCellFactory(listView -> new AnimalCell());
comboBox.setButtonCell(new AnimalCell());
comboBox.getSelectionModel().select(0);
stage.setScene(new Scene(comboBox));
stage.show();
}
public static void main(String[] args) {
launch(args);
}
}
StringConverter Implementation
An alternative to a cell factory definition is to provide the ComboBox with a StringConverter which can convert to and from a String and an object.
The StringConverter requires fromString and toString to be implemented, but the fromString implementation can just return null unless you also want the user to be able to perform text edits to edit the combo box value.
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.ComboBox;
import javafx.stage.Stage;
import javafx.util.StringConverter;
public class AnimalComboApp extends Application {
public record Animal(String name, int age, String color) {}
#Override
public void start(Stage stage) throws Exception {
ComboBox<Animal> comboBox = new ComboBox<>();
comboBox.getItems().setAll(
new Animal("Liam", 2, "Brown"),
new Animal("Emily", 5, "Gray"),
new Animal("Kian", 3, "Green")
);
comboBox.setConverter(new StringConverter<>() {
#Override
public String toString(Animal animal) {
return animal.name();
}
#Override
public Animal fromString(String string) {
return null;
}
});
comboBox.getSelectionModel().select(0);
Scene scene = new Scene(comboBox);
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch(args);
}
}
Options NOT to use
toString() implementation
Do not override toString() to customize the cells, that is an anti-pattern.
Use toString() for other purposes such as listing and debugging all the elements of the Animal class, and instead, use the appropriate methods, such as cell factories or string converters, for customizing the UI view of the Animal.
Placing nodes in the combo box list
You might also be tempted to try to put nodes directly in the ComboBox list (for example create Labels with the name of an object in each Label and then create a ComboBox<Label>).
Don't do this, as advised by the ComboBox API documentation section: "A warning about inserting Nodes into the ComboBox items list", it will create bugs in your application.

How To Display Objects in Java JList?

I'm trying to create a student registration system. In this system, students can see course name, course credit, and the instructor of the course by clicking the "Courses" button.For this purpose i have a Courses class, a database, a frame and a JList courslist.
ArrayList<Courses> aq = Database.allCourses();
//allCourses() is a static method in my Database class that returns fields from my Database as an ArrayList<Courses>
courselist.setListData(Driver.converToCoursesArray(aq));
//Driver.converttoCoursesArray() is a static method in my Driver class that takes a ArrayList<Courses> as a paramater and returns a Courses[] array.
Now, my problem is that in my frame, JList always seen like p1.Courses#4532
I've seen a similar problem when i was accidently trying to print an object with System.out.println(). But in this situation i convert the arraylist to an array and my JList holds objects(JList). So i'll be happy if you help me.

You need to override toString() in the Course class, such that it returns the name of the course you want to display.
Take a look at this example:
import javax.swing.*;
import java.awt.*;
public final class Example extends JFrame {
public Example() {
Course[] courses = {
new Course("Course 1"),
new Course("Course 2"),
new Course("Course 3")
};
JList<Course> courseJList = new JList<>(courses);
getContentPane().add(courseJList);
pack();
setMinimumSize(new Dimension(200, 200));
setVisible(true);
}
public static void main(String[] args) {
new Example();
}
}
final class Course {
private final String courseName;
public Course(final String courseName) {
this.courseName = courseName;
}
#Override
public String toString() {
return courseName;
}
}
This displays the following:

non-static JLabel cannot be referenced from static context while moving console println into GUI

Whatever I try to modify there's always a problem and the program won't run.
The thing is that my program works fine, when it's launched in the console, everything is ok, but when I try to make a GUI, and get text from console in the window, variables doesn't seem to work as they were.
The program is very simple, it has three packages like this:
//class SklepZoologiczny in package sklepzoologiczny
package sklepzoologiczny;
import javax.swing.JFrame;
import zwierzeta.*;
import magazyn.*;
public class SklepZoologiczny {
public static void main(String[] args) {
GUI GUI = new GUI();
GUI.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
GUI.pack();
GUI.setSize(300, 500);
GUI.setVisible(true);
GUI.setTitle("Appka Zaliczeniowa - Sklep Zoologiczny");
GUI.setResizable(false);
GUI.setLocationRelativeTo(null);
}
}
//class GUI in package sklepzoologiczny
package sklepzoologiczny;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import magazyn.*;
import zwierzeta.*;
public class GUI extends JFrame {
public JLabel l_imie, l_gatunek, l_rasa;
public JButton b_dodaj, b_usun, b_lista;
public JTextField tf_imie, tf_gatunek, tf_rasa;
public String imie, gatunek, rasa;
public ArrayList lista_psow, lista_kotow;
public String pies, kot, gatunek_zwierza;
public String imie_psa, rasa_psa;
public String imie_kota, rasa_kota;
public GUI() {
setLayout(new FlowLayout());
b_dodaj = new JButton("Uruchom Program");
add(b_dodaj);
l_imie = new JLabel("Text from console to GUI should go here");
add(l_imie);
event dodanie = new event();
b_dodaj.addActionListener(dodanie);
}
public class event implements ActionListener {
public void actionPerformed(ActionEvent dodanie) {
magazyn magazyn1 = new magazyn();
magazyn1.kasa = 0;
pies pies1 = new pies();
kot kot1 = new kot();
krolik krolik1 = new krolik();
pies1.ustawImie("Max");
kot1.ustawImie("Nuta");
krolik1.ustawImie("Filip");
pies1.ustawCene(200);
kot1.ustawCene(100);
krolik1.ustawCene(50);
pies1.ustawRase("Jamnik");
kot1.ustawRase("Perski");
krolik1.ustawRase("Mini_Lop");
pies1.ustawGatunek("pies");
kot1.ustawGatunek("kot");
krolik1.ustawGatunek("krolik");
System.out.println("Operacje Zakupu Zwierzat");
System.out.println("---");
magazyn1.dodajZwierza(pies1);
magazyn1.dodajZwierza(kot1);
magazyn1.dodajZwierza(krolik1);
magazyn1.StanSklepu();
System.out.println("Transkacje");
System.out.println("---");
magazyn1.sprzedajZwierza("Nuta");
magazyn1.StanSklepu();
}
}
}
//class magazyn in package magazyn
package magazyn;
import java.util.ArrayList;
import zwierzeta.*;
public class magazyn {
public float kasa;
ArrayList <zwierzeta> lista = new ArrayList(20);
public void dodajZwierza(zwierzeta i){
lista.add(i);
sklepzoologiczny.GUI.l_rasa.setText("Do sklepu dodano zwierza o imieniu: " + i.wezImie());
}
public void sprzedajZwierza(String i){
for(int j=0; j<lista.size(); j++){
if(lista.get(j).wezImie() == i){
kasa = kasa + lista.get(j).wezCene();
lista.remove(j);
System.out.println("Sprzedano: " + i);
}
}
}
public void StanSklepu(){
System.out.println("Aktualny stan sklepu:");
for(int i=0; i<lista.size(); i++){
System.out.println(lista.get(i).wezImie()+", " +lista.get(i).wezGatunek()+", " + lista.get(i).wezRase() + ", cena: " + lista.get(i).wezCene());
}
System.out.println("Stan kasy \t\t\t" + kasa);
}
}
//class zwierzeta in package zwierzeta
package zwierzeta;
public abstract class zwierzeta {
String imie, gatunek, rasa;
float cena;
/* public void checkProduct() throws ProductException{
if(isDamaged == true){
ProductException damaged = new ProductException();
damaged.setErrorMessage("Product is damaged:");
throw damaged;
}
}*/
public void ustawImie(String i){
imie = i;
}
public String wezImie(){
return imie;
}
public void ustawGatunek(String i){
gatunek = i;
}
public String wezGatunek(){
return gatunek;
}
public void ustawRase(String i){
rasa = i;
}
public String wezRase(){
return rasa;
}
public void ustawCene(float i){
cena = i;
}
public float wezCene(){
return cena;
}
}
There are also three classes in package zwierzeta which only extends zwierzeta with no code in it.
So the thing is, whatever I try to put in the dodajZwierza in magazyn.java, there's always an error which says that I can't use non-static variable l_rasa to reference in a static context. I don't know how to fix this, I tried to make class as static in GUI but it just gets worse with more errors.
How can I get the text to appear in the window instead of a console?

First of all - you better avoid using members with names identical to type names:
GUI GUI = new GUI();
You - and the JVM - are more than likely to get confused by this, not knowing whether you are trying to access the class type or the class instance when you later run something like:
GUI.setVisible(true);
Second, if you want to let one class access a member of another class, it is much better to provide a getter that returns (a reference to ) that member, instead of defining the member as static and let the other classes access it directly.

You seem to conflate classes and instances: you want to create an instance of class GUI and then pass this instance around to be able to use the instance rather than the class.
In your main method, you create an instance of class GUI:
GUI GUI = new GUI();
The variable which refers to this instance you call GUI, the same as the class. This is a very bad idea. Java naming conventions dictate that variable names start with a non-capital letter, so you should write:
GUI gui = new GUI();
and change the rest of the main method accordingly.
Now, this instance gui is what you want to use. You have to pass it to the methods where you use it, and then write for example
gui.l_rasa.setText(...);
By the way, your code becomes more maintainable if you make the member variables of a class private, and add getter and setter methods to access them.

You are trying to access non static variable defined in GUI class as:
public JLabel l_imie, l_gatunek, l_rasa;
Here:
sklepzoologiczny.GUI.l_rasa.setText
I dont see its being initialised, but you could define it as static in GUI class like:
public static JLabel l_rasa;//initialize it may be and that would resolve your issue.

How do I get the dynamic class name of an object?

So I have a List of Actors and I want to get each Actors dynamic class name.
For example here is my Actor list: People, Birds, Cows.
I want to get as result the same: "People, Birds, Cows" but without a name attribute in the Actors class. Is it possible?
Example code (here instead of list I used array) :
public Area map[][];
map[0][0] = new AntHillArea();
String name = map[0][0].getClass().getName(); //this results "Area" instead of AntHillArea
Edit: There was other problems with the code, getClass().getName() works fine. Thanks anyway.

String className = obj.getClass().getSimpleName();
Update:
public class Test {
public static void main(String[] args) {
Area map[][] = new Area[1][1];
map[0][0] = new AntHillArea();
String name = map[0][0].getClass().getSimpleName(); // returns "AntHillArea"
System.out.println(name);
}
}
class Area {
}
class AntHillArea extends Area {
}
Use getSimpleName method. It gives you only class and will remove any package if having.

You can do this:
class Dog
{
//code
public String getName()
{
return Dog.class.getName();
}
//better
#Override
public String toString()
{
return Dog.class.getName();
}
}
And similarly for each class. Or have a global one as mentioned in other answers as:
public static String getClassName(Class<?> clas){
return clas.getName();
}
To use Dog dog = new Dog(); getClassName(dog.class);

Multiple classes in single file

I'm having trouble putting multiple classes into a single file. For example, when my file looks like:
public class FirstClass() {}
public class SecondClass() {}
public class ThirdClass() {}
I get an error during compilation. I'm not quite sure what's causing this. Any ideas?

One Java file can consist of multiple classes with the restriction that only one of them can be public. As soon as you remove public keyword from your classes, you can combine them into a single Java file.

At the risk of spoon-feeding
Please read http://docs.oracle.com/javase/tutorial/java/javaOO/innerclasses.html
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class TheaterWindow extends JFrame
{
private JPanel pnlAdultTicketPrice, pnlAdultTicketsSold, pnlChildTicketPrice, pnlChildTicketsSold,
pnlCalculate, pnlMain;
private JLabel lblAdultTicketPrice, lblAdultTicketsSold, lblChildTicketPrice, lblChildTicketsSold;
private JTextField txtAdultTicketPrice, txtAdultTicketsSold, txtChildTicketPrice, txtChildTicketsSold;
private JButton btnCalculate;
public TheaterWindow()
{
// Sets window title
setTitle("Theater");
// Sets layout to BorderLayout
setLayout(new GridLayout(5,1));
// Specifies what happens when close button is clicked
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Builds the panels
buildPanels();
// Add the panels to the frame's content pane
add(pnlAdultTicketPrice);
add(pnlChildTicketPrice);
add(pnlAdultTicketsSold);
add(pnlChildTicketsSold);
add(pnlCalculate);
// Size the frame to fit all of the panels
pack();
// Display the window
setVisible(true);
}
private void buildPanels()
{
// Creates labels to display instructions
lblAdultTicketPrice = new JLabel("Adult ticket price");
lblChildTicketPrice = new JLabel("Child ticket price");
lblAdultTicketsSold = new JLabel("Adult tickets sold");
lblChildTicketsSold = new JLabel("Child tickets sold");
// Creates text fields that are 10 characters wide
txtAdultTicketPrice = new JTextField(10);
txtChildTicketPrice = new JTextField(10);
txtAdultTicketsSold = new JTextField(10);
txtChildTicketsSold = new JTextField(10);
// Creates button with caption
btnCalculate = new JButton("Calculate");
// Adds action listener to button
btnCalculate.addActionListener(new CalcButtonListener());
// Creates panels
pnlAdultTicketPrice = new JPanel();
pnlChildTicketPrice = new JPanel();
pnlAdultTicketsSold = new JPanel();
pnlChildTicketsSold = new JPanel();
pnlCalculate = new JPanel();
pnlMain = new JPanel();
// Adds elements to their proper panels
pnlAdultTicketPrice.add(lblAdultTicketPrice);
pnlAdultTicketPrice.add(txtAdultTicketPrice);
pnlChildTicketPrice.add(lblChildTicketPrice);
pnlChildTicketPrice.add(txtChildTicketPrice);
pnlAdultTicketsSold.add(lblAdultTicketsSold);
pnlAdultTicketsSold.add(txtAdultTicketsSold);
pnlChildTicketsSold.add(lblChildTicketsSold);
pnlChildTicketsSold.add(txtChildTicketsSold);
pnlCalculate.add(btnCalculate);
// Adds all of the above panels to a main panel
pnlMain.add(pnlAdultTicketPrice);
pnlMain.add(pnlChildTicketPrice);
pnlMain.add(pnlAdultTicketsSold);
pnlMain.add(pnlChildTicketsSold);
pnlMain.add(pnlCalculate);
}
private class CalcButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
// Creates object of Theater
Theater theater = new Theater();
// Sets the member variables of Theater to the user's input
theater.setAdultTicketPrice(Double.parseDouble(txtAdultTicketPrice.getText()));
theater.setChildTicketPrice(Double.parseDouble(txtChildTicketPrice.getText()));
theater.setAdultTicketsSold(Integer.parseInt(txtAdultTicketsSold.getText()));
theater.setChildTicketsSold(Integer.parseInt(txtChildTicketsSold.getText()));
// Creates DecimalFormat object for rounding
DecimalFormat dollar = new DecimalFormat("#.##");
// Display the charges.
JOptionPane.showMessageDialog(null, "Adult ticket gross: $" +
Double.valueOf(dollar.format(theater.getAdultGross())) + "\n" +
"Child ticket gross: $" + Double.valueOf(dollar.format(theater.getChildGross())) + "\n" +
"Adult ticket net: $" + Double.valueOf(dollar.format(theater.getAdultNet())) + "\n" +
"Child ticket net: $" + Double.valueOf(dollar.format(theater.getChildNet())) + "\n" +
"Total gross: $" + Double.valueOf(dollar.format(theater.getChildGross())) + "\n" +
"Total net: $" + Double.valueOf(dollar.format(theater.getTotalNet())));
}
}
public class Theater
{
private double PERCENTAGE_KEPT = 0.20;
private double adultTicketPrice, childTicketPrice;
private int adultTicketsSold, childTicketsSold;
public double getAdultGross()
{
return getAdultTicketPrice() * getAdultTicketsSold();
}
public double getAdultNet()
{
return PERCENTAGE_KEPT * getAdultGross();
}
public double getAdultTicketPrice()
{
return adultTicketPrice;
}
public int getAdultTicketsSold()
{
return adultTicketsSold;
}
public double getChildGross()
{
return getChildTicketPrice() * getChildTicketsSold();
}
public double getChildNet()
{
return PERCENTAGE_KEPT * getChildGross();
}
public double getChildTicketPrice()
{
return childTicketPrice;
}
public int getChildTicketsSold()
{
return childTicketsSold;
}
public double getTotalGross()
{
return getChildGross() + getAdultGross();
}
public double getTotalNet()
{
return getChildGross() + getChildNet();
}
public void setAdultTicketPrice(double adultTicketPrice)
{
this.adultTicketPrice = adultTicketPrice;
}
public void setAdultTicketsSold(int adultTicketsSold)
{
this.adultTicketsSold = adultTicketsSold;
}
public void setChildTicketPrice(double childTicketPrice)
{
this.childTicketPrice = childTicketPrice;
}
public void setChildTicketsSold(int childTicketsSold)
{
this.childTicketsSold = childTicketsSold;
}
}
}

Yes You can write your all classes in a single .java file, But you must have only one class public(if file name and class name same)
Example:
class A
{
}
class B
{
}
class C
{
}

I am assuming you are very beginner! Just copy paste all these contents in a single file TheaterDemo.java. And dont forget to remove all the public keyword in the beginning of class declaration.

One Java file can contain at most one top-level public class. That public top-level class can contain any number of public nested classes.
You can eliminate your compiler errors by any of the following approaches:
Moving the other classes into their own files. For example: FirstClass.java, SecondClass.java, and ThirdClass.java.
Nesting the classes whose name is not the file basename. For example:
public class FirstClass() {
public class SecondClass() {}
public class ThirdClass() {}
}
Removing the public qualifier from all but the one class whose name is the file basename. This approach has become less common after the introduction of nested classes in Java v1.1. For example, in file FirstClass.java, you could have:
public class FirstClass() {}
class SecondClass() {}
class ThirdClass() {}
From the Java Language Specification, section 7.6: Top Level Type Declarations:
If and only if packages are stored in a file system (§7.2), the host system may choose to enforce the restriction that it is a compile-time error if a type is not found in a file under a name composed of the type name plus an extension (such as .java or .jav) if either of the following is true:
The type is referred to by code in other compilation units of the package in which the type is declared.
The type is declared public (and therefore is potentially accessible from code in other packages).

Just remove public from all other class definition and paste the code into TheaterDemo.java file
public class TheaterDemo
{
public static void main(String[] args)
{
TheaterWindow theaterWindow = new TheaterWindow();
}
}
//Here class code after removing public
// Here another class code

I see you have already done that kind of implementation. Please refer
private class CalcButtonListener implements ActionListener
in your TheaterWindow class.
By doing this, you are creating inner classes i.e. CalcButtonListener is an inner class of TheaterWindow class. Some concept you can extend to other classes.

There is no restriction on the number of class files in a java file.
But we can’t have more than one public class per source code file. Also the name of the file must match the name of the public class. Like, a class declared as public class Dog { } must be in a source code file named Dog.java.
And files with no public classes can have a name that does not match any of the classes in the file.