GUI will not display

[JPDobner]

My code compiles and runs but the GUI will not display. I have tinkered with it but cannot get it to come up. Someone said I may be miscalling my GUI in this code, help?

Thank you.

import javax.swing.*;

import java.awt.event.*;

public class Application_MainRunInv extends JFrame {

private JTextArea txt;
private Inventory inv;
private int currentDisplay = 0;

public Application_MainRunInv() {
super("Pencil Warehouse");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // Prompts program to quit when closed
}

public void init() {
//Creates 3 Pencil Types
Brand p1 = new Brand(120, "Charcoal Pencil", 41, 1.97, "Stanford");
Brand p2 = new Brand(121, "Colored", 82, 1.49, "Stanford");
Brand p3 = new Brand(123, "Number2", 53, .97, "Woodward");

//Creates an inventory for the information
inv = new Inventory();
inv.add(p1);
inv.add(p2);
inv.add(p3);

inv.sort();

//Outputs the above information

for (int i = 0; i < inv.size(); i++) {
System.out.println("Pencil Number: " + inv.get(i).getPencilNumber());
System.out.println("Pencil Name: " + inv.get(i).getPencilName());
System.out.println("Pencil Stock: " + inv.get(i).getPencilStock());
System.out.println("Pencil Cost: $" + String.format("%.2f",inv.get(i).getPencilCost()));
System.out.println("Total Inventory Value: $" + String.format("%.2f",inv.get(i).TotalValue()));
System.out.println("Restocking-Fee: $" + String.format("%.2f",inv.get(i).RestockingFee()));
}


System.out.println("Total Inventory Value: $" + String.format("%.2f",inv.TotalValue()));

//Sets up the interface prior to button creation
JPanel panel = new JPanel();
txt = new JTextArea(15,40);
txt.setEditable(false);
panel.add(txt);

JButton original = new JButton("Original");
original.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
currentDisplay = 0;
displayPencil();
}
});
panel.add(original);
JButton previous = new JButton("Previous");
previous.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (currentDisplay > 0) currentDisplay--;
else currentDisplay = inv.size()-1;
displayPencil();
}
});
panel.add(previous);
JButton next = new JButton("Next");
next.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (currentDisplay < inv.size()-1) currentDisplay++;
else currentDisplay = 0;
displayPencil();
}
});
panel.add(next);
JButton end = new JButton("End");
end.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
currentDisplay = inv.size()-1;
displayPencil();
}
});

panel.add(end);
panel.add(new Graphic());

getContentPane().add(panel);

displayPencil();
}

public void displayPencil() {
txt.setText("Pencil Information:\n");
txt.append("Pencil Number: " + inv.get(currentDisplay).getPencilNumber() + "\n");
txt.append("Pencil Name: " + inv.get(currentDisplay).getPencilName() + "\n");
txt.append("Pencil Stock: " + inv.get(currentDisplay).getPencilStock() + "\n");
txt.append("Pencil Cost: $" + String.format("%.2f",inv.get(currentDisplay).getPencilCost()) + "\n");
txt.append("Total Inventory Value: $" + String.format("%.2f",inv.get(currentDisplay).TotalValue()) + "\n");
txt.append("Restocking-Fee: $" + String.format("%.2f",inv.get(currentDisplay).RestockingFee()) + "\n\n");
txt.append("Total Inventory Value: $" + String.format("%.2f",inv.TotalValue()));


}

public static void main(String args[]) {
Application_MainRunInv gui = new Application_MainRunInv();
gui.pack();
gui.setVisible(true);
}
//
}