Java application Problem - Net beans

I am exploring java IDE's right now i am starting with netbeans. I made a project that has two JFrame classes. I edited some code but i get a few errors. From what i can tell it has to do with something i did. I really cant see anything wrong? Maybe you can?

Errors:

Exception in thread "main" java.lang.NoClassDefFoundError: com/actvtimer/ActivityFrame$1
    at com.actvtimer.ActivityFrame.initComponents(ActivityFrame.java:49)
    at com.actvtimer.ActivityFrame.<init>(ActivityFrame.java:26)
    at com.actvtimer.ActivityFrame.main(ActivityFrame.java:155)
Caused by: java.lang.ClassNotFoundException: com.actvtimer.ActivityFrame$1
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
    ... 3 more

ActivityFrame.java:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/*
 * ActivityFrame.java
 *
 * Created on May 7, 2011, 5:29:14 PM
 */
package com.actvtimer;

import javax.swing.DefaultListModel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

/**
 *
 * @author Andrew
 */
public class ActivityFrame extends javax.swing.JFrame {
    DefaultListModel model = new DefaultListModel();

    /** Creates new form ActivityFrame */
    public ActivityFrame() {
        initComponents();
    }

    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jScrollPane2 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();
        jButton1 = new javax.swing.JButton();
        jScrollPane1 = new javax.swing.JScrollPane();
        jList1 = new javax.swing.JList();
        jButton2 = new javax.swing.JButton();
        jButton3 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Activity Timer");

        jTable1.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {

            },
            new String [] {
                "Activity", "Time Allowed", "Time Left"
            }
        ) {
            Class[] types = new Class [] {
                java.lang.String.class, java.lang.Integer.class, java.lang.String.class
            };
            boolean[] canEdit = new boolean [] {
                false, true, false
            };

            public Class getColumnClass(int columnIndex) {
                return types [columnIndex];
            }

            public boolean isCellEditable(int rowIndex, int columnIndex) {
                return canEdit [columnIndex];
            }
        });
        jScrollPane2.setViewportView(jTable1);

        jButton1.setText("Add Activity");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        jList1.setModel(model);
        jScrollPane1.setViewportView(jList1);

        jButton2.setText("Start Activity");

        jButton3.setText("Stop Activity");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jScrollPane2, javax.swing.GroupLayout.DEFAULT_SIZE, 464, Short.MAX_VALUE)
            .addGroup(layout.createSequentialGroup()
                .addComponent(jButton1)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 59, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jButton2)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jButton3)
                .addGap(108, 108, 108))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.sw开发者_如何学Pythoning.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 90, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jButton1)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                        .addComponent(jButton2)
                        .addComponent(jButton3))
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 68, Short.MAX_VALUE))
                .addContainerGap())
        );

        pack();
    }// </editor-fold>                        

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         

               AddActivityFrame addAct = new AddActivityFrame(this);
               addAct.setVisible(true);
               addAct.setResizable(false);

    }                                        

    public void addActivity(String name, int minutes) {
        model.addElement(name);


    }
    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
          try {
        // Set System L&F
        UIManager.setLookAndFeel(
            UIManager.getSystemLookAndFeelClassName());
    } 
    catch (UnsupportedLookAndFeelException e) {
       // handle exception
    }
    catch (ClassNotFoundException e) {
       // handle exception
    }
    catch (InstantiationException e) {
       // handle exception
    }
    catch (IllegalAccessException e) {
       // handle exception
    }

               ActivityFrame app = new ActivityFrame();
               app.setVisible(true);
               app.setResizable(false);

    }
    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JButton jButton3;
    private javax.swing.JList jList1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JTable jTable1;
    // End of variables declaration                   
}

---

NoClassDefFound means "No Class Definition Found".

NoClassDefFound is an error from the JVM when it cannot find a class required to run a Java program. This error could be caused by an actual missing class, but it is usually caused by a faulty CLASSPATH.

I'm guessing that your configuration for NetBeans wasn't setup correctly. The code doesn't seem to be the problem.