Q:

Creating objects depending on an Array

I've got an Array holding the amount of directories located in an another directory. However my problem is I have to create a JPanel for each folder.
For example:
File folder = new File("...");
File[] listOfFiles = folder.listFiles(); <- this contains the folders ({"folder1","folder2","folder3",...}).

Now I don't know how to fix this.
Some code I have written:
SystemAPI sapi = new SystemAPI(); <- custom written API  
File folder = new File(sapi.getHomeDir+"\\Documents\\*programname*\\default");  
File[] listOfFiles = folder.listFiles();

    try{
        for (int i = 0; i < listOfFiles.length; i++) {
            if (listOfFiles[i].isFile()) {
                System.out.println(listOfFiles[i].getName());
            } else if (listOfFiles[i].isDirectory()) {
                System.out.println(listOfFiles[i].getName());
            }
        }   
    }catch(Exception a){
        JOptionPane.showMessageDialog(null, "Error Occurred", "Error Dialog", JOptionPane.ERROR_MESSAGE);
    }

A:

You could do something like this (I made it using a layout provided by MigLayout but that can be changed)
import javax.swing.*;
import java.awt.*;
import net.miginfocom.swing.MigLayout;
import java.io.*;
import java.util.ArrayList;
import java.awt.event.*;
import javax.swing.event.*;
import javax.swing.JTabbedPane;

public class SimpleGUI
{
    public JFrame myMainWindow = new JFrame("Multtiple directories");

    JPanel[] guiPanelS = new JPanel[1000];
    JScrollPane[] guiJSP = new JScrollPane[1000];
    public JTabbedPane tabbedPane = new JTabbedPane();
    int pI = 0;
    String mainDirectory = "C:/Users/Daniel/Dropbox/Programming/Code/Notepad++/Java/Stack Overflow";
    String mainDirectoryName = new File(mainDirectory).getName();
    int indentForMainPanel = 30;
    String parseIndent = Integer.toString(indentForMainPanel);
    String lastDirOpen = mainDirectory;
    String lastDirOpenBut = mainDirectory;
    ArrayList<File> directoriesList = new ArrayList<File>();

    public void runGUI()
    {
        myMainWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        myMainWindow.setLayout(new GridLayout(1,1));

        listFilesHD(new File(mainDirectory),mainDirectoryName);

        final boolean showTabsHeader = false;
        tabbedPane.setUI(new javax.swing.plaf.basic.BasicTabbedPaneUI()
        {
            @Override
            protected int calculateTabAreaHeight(int tabPlacement, int horizRunCount, int maxTabHeight)
            {
                if(showTabsHeader)
                {
                    return super.calculateTabAreaHeight(tabPlacement, horizRunCount, maxTabHeight);
                }
                else
                {
                    return 0;
                }
            }
            protected void paintTabArea(Graphics g,int tabPlacement,int selectedIndex){}
        });

        myMainWindow.getContentPane().add(tabbedPane);
        tabbedPane.addChangeListener(new CustomChangeListener());

        myMainWindow.setVisible(true);
        myMainWindow.setBounds(10,10,500,500);
    }

    public void listFilesHD(File f,String dName)
    {
        MigLayout layout = new MigLayout("wrap", "[grow]");
        guiPanelS[pI] = new JPanel(layout);
        guiJSP[pI] = new JScrollPane(guiPanelS[pI]);
        JLabel currentDir = new JLabel("Current Directory: "+dName);
        guiPanelS[pI].add(currentDir,"align center");
        JLabel DirectoryName = new JLabel(dName);
        DirectoryName.setForeground(Color.BLUE);
        guiPanelS[pI].add(DirectoryName);
        File[] listOfFiles = f.listFiles();

        JLabel[] listsValues = new JLabel[listOfFiles.length];
        JButton[] tabSwitch = new JButton[listOfFiles.length];

        int i=0;
        int i2=0;
        for(File fileTemp:listOfFiles)
        {
            listsValues[i] = new JLabel(listOfFiles[i].getName());
            if(listOfFiles[i].isDirectory())
            {
                directoriesList.add(listOfFiles[i]);
                tabSwitch[i2] = new JButton(listOfFiles[i].getName());
                tabSwitch[i2].setOpaque(false); //These remove the button filling and border
                tabSwitch[i2].setContentAreaFilled(false);
                tabSwitch[i2].setBorder(null);
                tabSwitch[i2].setFocusable(false);
                tabSwitch[i2].setForeground(Color.RED);
                tabSwitch[i2].addActionListener(new openNewPaneActionListener());
                guiPanelS[pI].add(tabSwitch[i2],"gapLeft 30");
                i2++;
            }
            else if(listOfFiles[i].isFile())
            {
                guiPanelS[pI].add(listsValues[i],"gapLeft 30");
            }

            i++;
        }

        tabbedPane.addTab(f.getAbsolutePath(),guiJSP[pI]);
        guiJSP[pI].getVerticalScrollBar().setUnitIncrement(16);
        pI++;
    }

    public void listFilesSubD(File f,String dName,String dPath, String homeDirectory)
    {
        MigLayout layout = new MigLayout("wrap", "[grow]");
        guiPanelS[pI] = new JPanel(layout);
        guiJSP[pI] = new JScrollPane(guiPanelS[pI]);
        JLabel currentDir = new JLabel("Current Directory: "+dName);
        guiPanelS[pI].add(currentDir,"align center");
        JButton homeDirectoryName = new JButton(homeDirectory);
        homeDirectoryName.setForeground(Color.BLUE);
        homeDirectoryName.addActionListener(new backListener());
        homeDirectoryName.setOpaque(false); //These remove the button filling and border
        homeDirectoryName.setContentAreaFilled(false);
        homeDirectoryName.setBorder(null);
        homeDirectoryName.setFocusable(false);
        guiPanelS[pI].add(homeDirectoryName);

        if(!new File(lastDirOpenBut).getName().equals(mainDirectoryName))
        {
            JButton lastDirectoryName = new JButton(new File(lastDirOpenBut).getName());
            lastDirectoryName.setForeground(Color.GREEN);
            lastDirectoryName.addActionListener(new upOneListener());
            lastDirectoryName.setOpaque(false);
            lastDirectoryName.setContentAreaFilled(false);
            lastDirectoryName.setBorder(null);
            lastDirectoryName.setFocusable(false);
            guiPanelS[pI].add(lastDirectoryName,"gapLeft 30");

            File[] listOfFiles = f.listFiles();

            JLabel[] listsValues = new JLabel[listOfFiles.length];
            JButton[] tabSwitch = new JButton[listOfFiles.length];

            int i=0;
            int i2=0;
            for(File fileTemp:listOfFiles)
            {
                listsValues[i] = new JLabel(listOfFiles[i].getName());
                if(listOfFiles[i].isDirectory())
                {
                    directoriesList.add(listOfFiles[i]);
                    tabSwitch[i2] = new JButton(listOfFiles[i].getName());
                    tabSwitch[i2].setOpaque(false);
                    tabSwitch[i2].setContentAreaFilled(false);
                    tabSwitch[i2].setBorder(null);
                    tabSwitch[i2].setFocusable(false);
                    tabSwitch[i2].setForeground(Color.RED);
                    tabSwitch[i2].addActionListener(new openNewPaneActionListener());
                    guiPanelS[pI].add(tabSwitch[i2],"gapLeft 60");
                    i2++;
                }
                else if(listOfFiles[i].isFile())
                {
                    guiPanelS[pI].add(listsValues[i],"gapLeft 60");
                }
                i++;
            }
        }
        else
        {
            File[] listOfFiles = f.listFiles();

            JLabel[] listsValues = new JLabel[listOfFiles.length];
            JButton[] tabSwitch = new JButton[listOfFiles.length];

            int i=0;
            int i2=0;
            for(File fileTemp:listOfFiles)
            {
                listsValues[i] = new JLabel(listOfFiles[i].getName());
                if(listOfFiles[i].isDirectory())
                {
                    directoriesList.add(listOfFiles[i]);
                    tabSwitch[i2] = new JButton(listOfFiles[i].getName());
                    tabSwitch[i2].setOpaque(false); //These remove the button filling and border
                    tabSwitch[i2].setContentAreaFilled(false);
                    tabSwitch[i2].setBorder(null);
                    tabSwitch[i2].setFocusable(false);
                    tabSwitch[i2].setForeground(Color.RED);
                    tabSwitch[i2].addActionListener(new openNewPaneActionListener());
                    guiPanelS[pI].add(tabSwitch[i2],"gapLeft 30");
                    i2++;
                }
                else if(listOfFiles[i].isFile())
                {
                    guiPanelS[pI].add(listsValues[i],"gapLeft 30");
                }
                i++;
            }
        }

        if(tabbedPane.indexOfTab(dPath)==-1)
        {
            tabbedPane.addTab(dPath,guiJSP[pI]);
        }

        guiJSP[pI].getVerticalScrollBar().setUnitIncrement(16);
        pI++;
    }

    public static void main(String[] args)
    {
        SimpleGUI sG = new SimpleGUI();
        sG.runGUI();
    }

    class openNewPaneActionListener implements ActionListener
    {
        @Override
        public void actionPerformed(ActionEvent e)
        {
            lastDirOpenBut = tabbedPane.getTitleAt(tabbedPane.getSelectedIndex());
            String butSrcTxt = "";
            Object source = e.getSource();
            if (source instanceof JButton) 
            {
                JButton btn = (JButton)source;
                butSrcTxt = btn.getText();
            }

            boolean tF = false;
            File fMain = new File("");
            for(File f:directoriesList)
            {
                if(f.getName().equals(butSrcTxt))
                {
                    fMain = f;
                    tF = true;
                }
            }

            if(tF)
            {
                if(tabbedPane.indexOfTab(fMain.getAbsolutePath())==-1)
                {
                    listFilesSubD(fMain, butSrcTxt, fMain.getAbsolutePath(),mainDirectoryName);
                }

                tabbedPane.setSelectedIndex(tabbedPane.indexOfTab(fMain.getAbsolutePath()));
            }

        }
    }

    class upOneListener implements ActionListener
    {
        @Override
        public void actionPerformed(ActionEvent e)
        {
            tabbedPane.setSelectedIndex(tabbedPane.indexOfTab(lastDirOpen));
        }
    }

    class CustomChangeListener implements ChangeListener
    {
        @Override
        public void stateChanged(ChangeEvent e)
        {
            lastDirOpen = tabbedPane.getTitleAt(tabbedPane.getSelectedIndex());
            int endIndex = lastDirOpen.lastIndexOf(Character.toString((char) 92));
            if (endIndex != -1)
            {
                lastDirOpen = lastDirOpen.substring(0, endIndex);
            }
        }
    }

    class backListener implements ActionListener
    {
        @Override
        public void actionPerformed(ActionEvent e)
        {
            tabbedPane.setSelectedIndex(0);
        }
    } 
}

The code produces a simple GUI (as shown in the picture below). The picture shows the directory currently open. The blue button is the home directory which opens when clicked. The files in the open directory are black. The sub directories are red buttons which when clicked open a new panel with the contents of that directory and finally the green button is the directory above the one currently open. For example if you are in C:\\D\B when the green button is clicked you would enter C:\\D.
All the panels are on a JScrollPane so you do not need to worry about the amount of files in the directory. You can now adapt this code to your own. I would also suggest you get MigLayout if you don't have it already so you can see how this little program works.

