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Java - How do I modify static ArrayList in one class with an ActionListener in another class?

I'm trying to modify a static ArrayList, "selectList," in the class "AnimalGUI."
I have to take user input through Java GUI so I implemented JFrame and all that in another class.
I encounter the problem when I pass the ArrayList to an ActionListener that exists in a different class, "HandleGUI." The ActionListener cannot modify the static ArrayList for some reason.
I know it's not working because I tried to print the ArrayList's content after, supposedly, modifying it and the system printed nothing.
Below is the class Animal GUI, nothing special to focus on besides the ArrayList "selectList" at the bottom of the code.
public class AnimalGUI {
public static void main(String[] args) {
AnimalGUI a = new AnimalGUI();
HandleGUI h = new HandleGUI();
h.initialisation();
a.printSelectList();
}
//Print selectList
void printSelectList(){
for(int x: selectList){
System.out.println(x);
}
}
static ArrayList<Integer> selectList = new ArrayList<Integer>();
static ArrayList<Animal> aniList = new ArrayList<Animal>();
static String[][] Forest = new String[15][15];
}
Below is the subclass "HandleGUI".
You can ignore most of the Java GUI components. The important part here is the ActionListener "selectListener."
public class HandleGUI{
JFrame menu = new JFrame("Startup Menu");
JPanel panelA = new JPanel();
JCheckBox cCB, dCB, fCB, hCB, lCB, tCB, uCB, wCB;
JButton cBT, dBT, fBT, hBT, lBT, tBT, uBT, wBT, start;
//Constructor
public HandleGUI(){
//Declare all the JCheckBoxes.
cCB = new JCheckBox("Cat");
dCB = new JCheckBox("Dog");
fCB = new JCheckBox("Fox");
hCB = new JCheckBox("Hippo");
lCB = new JCheckBox("Lion");
tCB = new JCheckBox("Tiger");
uCB = new JCheckBox("Turtle");
wCB = new JCheckBox("Wolf");
//Declare all the JButtons.
cBT = new JButton("Pick an alternative icon.");
dBT = new JButton("Pick an alternative icon.");
fBT = new JButton("Pick an alternative icon.");
hBT = new JButton("Pick an alternative icon.");
lBT = new JButton("Pick an alternative icon.");
tBT = new JButton("Pick an alternative icon.");
uBT = new JButton("Pick an alternative icon.");
wBT = new JButton("Pick an alternative icon.");
start = new JButton("Start");
//Declare JFrame and set its size.
//Make the startup menu display in centre of monitor.
menu.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
menu.setSize(300, 300);
Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
menu.setLocation(dim.width/2-menu.getSize().width/2, dim.height/2-menu.getSize().height/2);
}
//Generates a setup menu that allows user to select animals to be included in the simulation.
public void initialisation(){
//Make the startup menu display in centre of monitor.
Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
menu.setLocation(dim.width/2-menu.getSize().width/2, dim.height/2-menu.getSize().height/2);
//Set the JPanel to grid layout so elements on both columns align.
panelA.setLayout(new GridLayout(8, 2, 5, 5));
//Add the elements into JPanel.
panelA.add(cCB);
panelA.add(cBT);
panelA.add(dCB);
panelA.add(dBT);
panelA.add(fCB);
panelA.add(fBT);
panelA.add(hCB);
panelA.add(hBT);
panelA.add(lCB);
panelA.add(lBT);
panelA.add(tCB);
panelA.add(tBT);
panelA.add(uCB);
panelA.add(uBT);
panelA.add(wCB);
panelA.add(wBT);
//Add the Panel to the Frame.
menu.getContentPane().add(panelA, BorderLayout.CENTER);
menu.getContentPane().add(start, BorderLayout.SOUTH);
//Make Frame visible.
menu.setVisible(true);
start.addActionListener(new selectListener());
}
class selectListener implements ActionListener{
public void actionPerformed(ActionEvent e){
AnimalGUI a = new AnimalGUI();
if(cCB.isSelected())
a.selectList.add(0);
if(dCB.isSelected())
a.selectList.add(1);
if(fCB.isSelected())
a.selectList.add(2);
if(hCB.isSelected())
a.selectList.add(3);
if(lCB.isSelected())
a.selectList.add(4);
if(tCB.isSelected())
a.selectList.add(5);
if(uCB.isSelected())
a.selectList.add(6);
if(wCB.isSelected())
a.selectList.add(7);
menu.setVisible(false);
}
}
}

Looks like conditions in your selectListener are not met. So, the issue is not in static list not modifyable, but that program doesn't enter any if statement:
if(cCB.isSelected())
a.selectList.add(0);
.....

You are calling static fields from objects.
Instead of
AnimalGUI a = new AnimalGUI();
<...>
a.selectList.add(0);
Try
AnimalGUI.selectList.add(0);

How can I pass an ArrayList between two separate JTabbedPanes

I have a program utilizing JTabbedPane. On one pane I have a button that updates an arrayList of objects based on input from the same pane.
What I would like to happen is have the second pane update itself with the object information based on the arrayList in the first pane.
However, I am not sure how to pass the list between the panes. Is there some way to push the array to pane #2 when the update button on the first pane is pressed?
Here is the main file. Instantiating the two tabs
public class Assignment6 extends JApplet
{
private int APPLET_WIDTH = 650, APPLET_HEIGHT = 350;
private JTabbedPane tPane;
private StorePanel storePanel;
private PurchasePanel purchasePanel;
private ArrayList computerList;
public void init()
{
computerList = new ArrayList();
storePanel = new StorePanel(computerList, purchasePanel);
purchasePanel = new PurchasePanel(computerList);
tPane = new JTabbedPane();
tPane.addTab("Store Inventory", storePanel);
tPane.addTab("Customer Purchase", purchasePanel);
getContentPane().add(tPane);
setSize (APPLET_WIDTH, APPLET_HEIGHT); //set Applet size
}
}
The first panel instantiates a button listener that applies all of the logic to the array list "compList"
private class ButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
//Add Computer to list
Computer comp = new Computer();
comp.setBrandName(brandField.getText());
comp.setPrice(Double.parseDouble(priceField.getText()));
comp.setMemory(Integer.parseInt(memoryField.getText()));
comp.setCPU(typeField.getText(), Integer.parseInt(speedField.getText()));
compList.add(comp);
}
stringField.setText(listString);
alertLabel.setText("Computer Added");
}
}
Here is the other pane. The for loop at the end is what I need to push the arrayList to. After it receives the list, it populates a box with a checkbox for each object in the list
public PurchasePanel(ArrayList compList)
{
west = new JPanel();
east = new JPanel();
totalField = new JTextField();
this.compList = compList;
setLayout(new GridLayout(0,2));
add(west);
add(east);
east.setLayout(new BorderLayout());
east.add(currentTotalLabel, BorderLayout.NORTH);
east.add(totalField, BorderLayout.CENTER);
west.setLayout( new BoxLayout(west, BoxLayout.Y_AXIS));
for(Object c : compList){
System.out.println("Made it");
NumberFormat fmt = NumberFormat.getCurrencyInstance();
String str = ("BrandName:" + (((Computer) c).getBrandName() +"CPU:" + (((Computer) c).getCPU() +"Memory:" + ((Computer) c).getMemory() + "M" +"Price:" + fmt.format(((Computer) c).getPrice()))));
JCheckBox chk = new JCheckBox(str);
west.add(chk);
}
}
}

You can use the same listener used to update the first ArrayList, to update the second pane. Something like:
jButton1.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
// Update the first ArrayList
// Update the second pane
}

JAVA Display item from JList in JLabel

public class ListComboBox extends JFrame {
private String MIS = "MULTIPLE_INTERVAL_SELECTION";
private String SIS = "SINGLE_INTERVAL_SELECTION";
private String SS = "SINGLE_SELECTION";
final int COUNTRIES = 9;
private String[] countries = {"Canada", "China", "Denmark",
"France", "Germany", "India", "Norway", "United Kingdom",
"United States of America"};
private JList<String> jlst = new JList<String>(countries);
private JLabel comboLabel = new JLabel("Choose Selection Mode: ");
private JComboBox jcbo = new JComboBox();
//to hold country labels
private JLabel countryLabel = new JLabel();
public static void main(String[] args) {
ListComboBox frame = new ListComboBox();
frame.setSize(400, 200);
frame.setTitle("Exercise 17.14");
frame.setLocationRelativeTo(null); // Center the frame
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
public ListComboBox() {
//Adding selection option to combobox
jcbo.addItem(MIS);
jcbo.addItem(SIS);
jcbo.addItem(SS);
// Register listener combobox
jcbo.addItemListener(new ItemListener() {
#Override
public void itemStateChanged(ItemEvent e) {
if (e.getItem() == MIS) {
jlst.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
}
if (e.getItem() == SIS) {
jlst.setSelectionMode(ListSelectionModel.SINGLE_INTERVAL_SELECTION);
}
if (e.getItem() == SS) {
jlst.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
}
}
});
//Combobox panel
JPanel combopanel = new JPanel(new FlowLayout());
combopanel.add(comboLabel);
combopanel.add(jcbo);
add(combopanel, BorderLayout.NORTH);
//List panel
JScrollPane listpanel = new JScrollPane(jlst);
add(listpanel, BorderLayout.CENTER);
//Bottom label panel
final JPanel labelpanel = new JPanel();
labelpanel.add(countryLabel);
add(labelpanel, BorderLayout.SOUTH);
//List listener
jlst.addListSelectionListener(new ListSelectionListener() {
#Override
public void valueChanged(ListSelectionEvent e) {
StringBuilder sb = new StringBuilder(64);
int[] indices = jlst.getSelectedIndices();
int i;
for (i = 0; i < indices.length; i++) {
if (sb.length() > 0) {
sb.append(", ");
}
sb.append(countries[indices[i]]);
}
countryLabel.setText(sb.toString());
}
});
}
}
Good day, I need your help.
What I need code to do: Add selected country names from the list with scroll bar to the label below the list, remove them as they are unselected in the list.
List selection mode can be switched in JComboBox on top.
Everything works fine, but I cannot figure out the way for country names to properly appear inside the label.
Any tips on how I might accomplish that?
Thanks!
UPDATED!

setName is used for internal identification of the component. Imagin you've been give a list of components, all you know is you need to find the one with some unique identifier, that identifier is supplied via the name property. It has no effect on the output of the component.
You need to use the setText method to change what is displayed on the screen.
The next problem you'll have is setText is a replacement method. That is, it will replace what ever was previously applied with the new value. What might need to do is build a temporary String of the values you want to display and then apply that value to the label, for example...
StringBuilder sb = new StringBuilder(64);
for (i = 0; i < indices.length; i++) {
if (sb.length() > 0) {
sb.append(", ");
}
sb.append(countries[indices[i]]);
}
countryLabel.setText(sb.toString());

To set text on JLabel use countryLabel.setText instead of countryLabel.setName. Another issue is that in the posted code countryLabel is not added to the frame. I assume it should go into labelpanel, but this part is commented out.
Some other observations:
Do not mix light weight and heavy weight components. See Mixing Heavyweight and Lightweight Components. Instead of ScrollPane use JScrollPane, for example:
JScrollPane listpanel = new JScrollPane(jlst);
Also there is no need to revalidate() the container when you set text on JLabel. The label will be refreshed as a result of setText() method.

Deleting selected checkboxes using java swing

I am new to java swing. I have a code that generates checkboxes. I want to have a button somewhere in my frame, which on clicking, should delete the selected checkbox entries. Here is what I have so far.
public class Scroll extends JPanel {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable(){
public void run() {
createAndShowGUI();
}
});
}
public static void createAndShowGUI() {
JFrame frame = new JFrame("JFrame with ScrollBar");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComponent newContentPane = new ResultButtonBar();
newContentPane.setOpaque(true);
JScrollPane scrollPane = new JScrollPane(newContentPane);
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
frame.getContentPane().add(scrollPane);
frame.setSize(800, 800);
frame.setVisible(true);
JButton startButton = new JButton("Start");
frame.add(startButton, BorderLayout.SOUTH);
startButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
JOptionPane.showMessageDialog(null, "basdsadad");
}
});
}
}
and the new ResultButtonBar().java
public class ResultButtonBar extends JPanel {
private HashMap<JCheckBox, ArrayList<Integer>> map = new HashMap<>();
private JLabel _label;
private static final int MAX_CHECKS = 1000;
public ResultButtonBar() {
super();
JButton btn = new JButton();
btn.setVisible(true);
JCheckBox checkBox;
Random r = new Random();
JPanel checkPanel = new JPanel(new GridLayout(0, 1));
_label = new JLabel("You selected nothing");
checkPanel.add(_label);
for (int i = 0; i < MAX_CHECKS; i++) {
StringBuilder sb = new StringBuilder();
ArrayList<Integer> a = new ArrayList<>();
for (int j = 0; j < 2; j++) {
Integer temp = (r.nextInt()) % 100;
a.add(temp);
sb.append(temp).append(" ");
}
checkBox = new JCheckBox(sb.toString().trim());
checkBox.setName("CheckBox" + i);
map.put(checkBox, a);
checkPanel.add(checkBox);
}
add(checkPanel);
}
}

First of all, keep all your check boxes in an ArrayList so you will have a reference to them when you need it.
Then, add a JButton wherever you need. Then iterate over this ArrayList and call invalidate() on the component which contains your check boxes. Next statement would be to call the remove() method on the container; the checkPanel.
Alternatively, you may call removeAll() if all the components in the container are check boxes and you want to remove them.
The alternative pointed by StanislavL is also a good one if you have a lot of different components along with check boxes

I can think of two approaches:
if You are maintaining one JPanel instance which contains only the instances of JCheckBox, then you can first get all the checkbox's using panel.getComponents() method, check their selection state and depending on the state remove it by calling panel.remove(component). For example:
Component checkBox[] = checkBoxPanel.getComponents();
for(Component c:checkBox)
if(((JCheckBox)c).isSelected())
checkBoxPanel.remove(c);
checkBoxPanel.revalidate();
checkBoxPanel.repaint();
The last call revalidate() and repaint() on the checkBoxPanel is important for reflecting changes on the layout and graphics rendering of the components.
You can use ItemListener with the instances of JCheckBox to do things on selection state change. Use an instance of ArrayList<JCheckBox> to add the selected checkBox to the list. However you should use an implemented ItemListener: MyItemListener implements ItemListener and create one instance and add this instances to all the checkboxes to react on state change. You can use event source e.getSource() to get the JCheckBox instance on which the ItemEvent is performed.
Tutorial resource:
How to Write an Item Listener

How to refresh JScrollPane

My main frame contains JScrollPane which lists some objects. Through menu (pop up frame) I create new object and I want to list this object in the JScrollPane (which is created in a constructor of DemoFrame class). How can I do it?
Part of my constructor in DemoFrame
ArrayList<Item> i = g.getAllItems();
Vector allItemsVector = new Vector(i);
JList items = new JList(allItemsVector);
panel.add( new JScrollPane( items ))
In pop up frame I add new object to 'g' object in that case. Have I designed it wrong?

A lot depends on information that you haven't told us, for instance just what is the JScrollPane holding? A JTable? A JList? The key will be to update the component being held by the JScrollPane and then revalidate and repaint this component.
Edit
You need to have a reference to the JList, so it should be declared outside of your constructor. For instance:
// GUI class
public class GuiClass {
private JList items; // declare this in the *class*
// class's constructor
public GuiClass() {
ArrayList<Item> i = g.getAllItems();
Vector allItemsVector = new Vector(i);
// JList items = new JList(allItemsVector); // don't re-declare in constructor
items = new JList(allItemsVector);
panel.add( new JScrollPane( items ))
}
Then later in your menu's listener code you can add an item to the items JList as needed.

This was a problem for me as well. A quick workaround is remove the JScrollPane from the panel, make your changes then readd it. Many may deem it inefficient, but it works with no significant change to runtime
JPanel panel = new Jpanel();
JList list = new JList({"this", "is", "a test", "list"});
JScrollPane sPane = new JScrollPane();
public void actionPerformed(ActionEvent e) {
if (resultsPane!=null){
panel.remove(sPane);
}
sPane = updatePane(list);
panel.add(sPane);
}
public void updatePane(String[] newListItems) {
DefaultListModel model = new DefaultListModel();
for(int i = 0; i < newListItems.length; i++) {
model.addElement(newListItems[i]);
}
JList aList = new JList(model);
JScrollPane aPane = new JScrollPane(aList);
}

Assuming I understood the question correctly:
You have a JFrame with a JScrollPane. And the JScrollPane has a JList.
The JList has a set of strings in it and this shows fine, but later you want to update the list and have it update in the JFrame view, but when you do update the list nothing happens to visualisation?
I had the same problem and how I got it to work was to set the content of the JList using a DefaultListModel. Instead of updating the contents of the JList, I update the contents in the DefaultListModel and then set the JList content to the model content when everything has been added. Then call the JScrollPane repaint function
//Declare list and pane variables up here so that we have a reference
JList<String> list;
JScrollPane pane;
//Set up the frame content
void SetupFrame() {
//instantiate the list
list = new JList();
//sets up the scroll pane to take the list
pane = new JScrollPane();
pane.setViewportView(list);
pane.setBounds(10, 10, 200, 80);
//adds the scrollpane to the frame
add(pane);
//update the list of strings
UpdateList();
}
//Updates the contents of the list (call this whenever you want to update the list)
void UpdateList() {
//model used to update the list
DefaultListModel model = new DefaultListModel();
//Update the contents of the model
for (int i = 0; i < 10; i++)
model.addElement("Test value");
//update the list using the contents of the model
connectionLabels.setModel(model);
//repaint the scrollpane to show the new list content
pane.repaint();
}