Solve Java JLabel Problem: Display Output on mainPanel

[clook]

i am trying to display the output in a jlabel. I have created individual jlabels for the package ID, weight, and shipping cost and tried to display them with the mainPanel:

import javax.swing.*;

import java.awt.event.*;
public class shippingCharge extends JFrame implements ActionListener
{

	//objects and data types created here
	JPanel mainPanel = new JPanel();
	JTextField packageIdentificationTextField = new JTextField(6);
	JTextField poundsTextField = new JTextField(10);
	JTextField ouncesTextField = new JTextField(10);
	JButton displayButton = new JButton("Calculate  ");
	
	
	//Variables
	String packageIdentificationString;
	double poundDouble, ouncesDouble, poundToOunceOuncesDouble, shippingCostDouble;	public static void main(String[] args)
	{
		shippingCharge shippingTotal = new shippingCharge();
	}
		
	public shippingCharge()
	{
		designFrame();
		setSize(500,500);
		setVisible(true);
		
	}
	
	public void designFrame()
	{
		mainPanel.add(new JLabel("Package ID"));
		mainPanel.add(packageIdentificationTextField);
		mainPanel.add(new JLabel("Pounds"));
		mainPanel.add(poundsTextField);
		mainPanel.add(new JLabel("Ounces"));
		mainPanel.add(ouncesTextField);
		mainPanel.add(displayButton);
		
		
        add(mainPanel);
		//add listener to the  object
        packageIdentificationTextField.addActionListener(this);
		displayButton.addActionListener(this);
		
	}
	
	public void getInput()
	{
		packageIdentificationString = packageIdentificationTextField.getText();
		poundDouble = Double.parseDouble(poundsTextField.getText()); 
		ouncesDouble = Double.parseDouble(ouncesTextField.getText());
		
	}
	
	public void calculateShipping()
	{
		final double SHIPPING_RATE = .12;
		final double OUNCES_PER_POUND = 16;
		poundToOunceOuncesDouble = poundDouble * OUNCES_PER_POUND;
		shippingCostDouble = (poundToOunceOuncesDouble + ouncesDouble) * SHIPPING_RATE;
		
	}

	public void actionPerformed(ActionEvent evt)
	{
		getInput();
		calculateShipping();
		displayOutput();
		
		
	}
	
	public void displayOutput()
	{
		
	mainPanel.add(new JLabel("Package ID:" + packageIdentificationString));
        mainPanel.add(new JLabel("Weight:" + poundDouble + "lbs" + ouncesDouble + "oz."));
        mainPanel.add(new JLabel("Shipping Cost:" + shippingCostDouble));
	
			
	}
}

here is the code but the output labels aren't showing up. what gives? does it have something to do with positioning?

 

[monjaraz85]

Have you tried NetBeans?? You can graphically make the applet/gui of the program you are writing, it is a lot easier than just writing code. All you have to do is make it and add functionality to the buttons.