import javax.swing.*;
import java.awt.event.*;

public class FirstWindow extends JFrame{
	private JLabel lblQuantity;
	private JLabel lblPrice;
	private JTextField txtQuantity;
	private JTextField txtPrice;
	private JTextField txtResult;
	private JButton btnCalculate;
	private JPanel panel;
	
	public FirstWindow()
	{
		super("First Application!!!");
		setSize(250,300);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setVisible(true);
		buildPanel();
		add(panel);
		//pack();
	}
	
	public void buildPanel()
	{
		panel = new JPanel();
		lblQuantity = new JLabel("Enter a quantity");
		lblPrice = new JLabel("Enter a price");
		txtQuantity = new JTextField("test", 15);
		txtPrice = new JTextField("test", 15);
		btnCalculate = new JButton("Calculate!");
		txtResult = new JTextField(10);
		panel.add(lblQuantity);
		panel.add(txtQuantity);
		panel.add(lblPrice);
		panel.add(txtPrice);
		panel.add(txtResult);
		panel.add(btnCalculate);
		btnCalculate.addActionListener(new CalcButtonListener());
	}
	
	private class CalcButtonListener implements ActionListener
	{
		public void actionPerformed(ActionEvent e)
		{
			String strQuantity = txtQuantity.getText();
			String strPrice = txtPrice.getText();
			double result = Double.parseDouble(strQuantity) * Double.parseDouble(strPrice);
			txtResult.setText(result + "");
			
		}
	}
}