parsing from JTextField to double

[Bart Simpsong]

Ok, my program suppose to convert a number(pounds) into kilograms. Two JTextField and one Button. I am not sure how to parse the value from JTextField into double but this is what I have so far. Thank you for any help. This is not working, here is the error message:

Exception in thread "main" java.lang.NumberFormatException: empty String
        at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:99
4)
        at java.lang.Double.parseDouble(Double.java:510)
        at ButtonFrame.<init>(ButtonFrame.java:22)
        at ButtonTest.main(ButtonTest.java:5)
Press any key to continue . . .

import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JOptionPane;
import javax.swing.JTextField;

public class ButtonFrame extends JFrame{
	private JButton plainJButton;
	private JTextField textField1;
	private JTextField textField2;

	double result=0.0;
	double kg=0.45359237;

	public ButtonFrame(){
		super("Testing buttons");
		setLayout( new FlowLayout() );

		textField1 = new JTextField( 10 );
		double s = Double.parseDouble(textField1.getText());
		add( textField1 );

		textField2 = new JTextField( 10 );
		textField2.setEditable(false);
		add( textField2 );

	result = s * kg;//Double.parseDouble(textField1.getText()); // * kg

		plainJButton = new JButton("Addition Button");
		add( plainJButton );

		ButtonHandler handler = new ButtonHandler();
		plainJButton.addActionListener( handler );
	}

	private class ButtonHandler implements ActionListener{
		public void actionPerformed( ActionEvent event ){

			JOptionPane.showMessageDialog(null, "The conversion is"+ result,
				"of a value", JOptionPane.PLAIN_MESSAGE);
		}
	}
}

[Rob Spoor]

Welcome to the Ranch! Can you please UseCodeTags next time? I've added them for you this time.

Now, to the problem.

textField1 = new JTextField( 10 );   
double s = Double.parseDouble(textField1.getText());

The first line does not create a text field with contents "10" but a text field that will be large enough to show 10 characters. Its content is still empty (""). To get a JTextField to show the value "10" you must a) use textField.setText("10"), or b) create it using a String value (new JTextField("10")).

[Rob Camick]

double s = Double.parseDouble(textField1.getText());   

That code is in the wrong place. You want that code to be executed when the user does some action. So I guess that code and your conversion code should be added to your ActionListener. That is when the user is finished typing the number they want converted, they will click on a button to get the result.