How do I create an arraylist in and add and view it with buttons? - user-interface

Question

I'm trying to make a GUI program that enters and removes cars from an arraylist and displays the cars using JButtons. I am unable to get the arraylist to print from clicking on one of the buttons. I'm also unsure if my arraylist is made correctly. Any help would be greatly appreciated.
import java.util.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class Window extends JFrame {
public Window() {
super ("Rent-a-Car");
setSize(400, 100);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
JPanel p = new JPanel();
JButton b1 = new JButton("Add Car");
JButton b2 = new JButton("Rent Car");
JButton b3 = new JButton("Library");
p.add(b1);
p.add(b2);
p.add(b3);
add(p);
final ArrayList<String> cars = new ArrayList<String>();
cars.add("Audi");
cars.add("VolksWagon");
cars.add("Mercedes");
cars.add("BMW");
cars.add("Ford");
cars.add("Subaru");
cars.add("Lexus");
cars.add("Acura");
cars.add("Nissan");
b1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
Scanner sc = new Scanner(System.in);
JOptionPane.showInputDialog("Enter car model");
String model = sc.next();
JOptionPane.showMessageDialog(null, "Car added");
cars.add(model);
}
});
/*b3.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
for(int i=0 < cars.size(); i++) {
System.out.println();
}
}
});*/
}
}

Answer 1

In your ActionListener for b1 you're trying to scan it from the wrong place. If you run this, you've probably noticed that the JOptionPane doesn't do anything when you submit a car with the add button. However, if you enter a string into the terminal, an dialog will pop up saying "Car added". This is because Scanner sc is scanning System.in! This is not meant for GUIs.
Fortunately, it's really simple to get input from a JOptionPane.
EDIT: Added a few things like a JTextArea in a JScrollPane that is easy to append to and changed it to a simple GridLayout.
I also moved the ActionListeners into an inner class so that you don't clutter up your code with anonymous functions everywhere. It's also a bit easier to add stuff with the (e.getSource()) conditionals, too.
Set model equal to the result of showInputDialog as such:
import java.util.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.GridLayout;
import javax.swing.*;
public class Window extends JFrame {
private JPanel p;
private JButton b1, b2, b3;
private JTextArea textArea;
private JScrollPane scrollPane;
private ArrayList<String> cars;
public Window() {
super ("Rent-a-Car");
setLayout(new GridLayout(2, 1));
setSize(400, 100);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
p = new JPanel();
b1 = new JButton("Add Car");
b2 = new JButton("Rent Car");
b3 = new JButton("Library");
b1.addActionListener(new ButtonListener());
b2.addActionListener(new ButtonListener());
b3.addActionListener(new ButtonListener());
textArea = new JTextArea("");
textArea.setEditable(false);
scrollPane = new JScrollPane(textArea);
p.add(b1);
p.add(b2);
p.add(b3);
add(p);
//add(textArea);
add(scrollPane);
cars = new ArrayList<String>();
cars.add("Audi");
cars.add("VolksWagon");
cars.add("Mercedes");
cars.add("BMW");
cars.add("Ford");
cars.add("Subaru");
cars.add("Lexus");
cars.add("Acura");
cars.add("Nissan");
}
public void displayText(String s) {
textArea.append(s + "\n");
textArea.setCaretPosition(textArea.getDocument().getLength());
}
private class ButtonListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (e.getSource() == b1) {
String model = JOptionPane.showInputDialog("Enter car model");
cars.add(model);
displayText("Added car: " + model);
}
else if (e.getSource() == b2) {
//add something later
}
else if (e.getSource() == b3) {
for (String car : cars) {
displayText(car);
}
}
}
}
}