“线程中的异常”；AWT-EventQueue-0“；java.lang.NoClassDefFoundError:测试/可视化

我编译并运行我的程序没有问题，当我在一个小时后打开Netbeans时，我在线程“AWT-EventQueue-0”java.lang.NoClassDefFoundError:test/Visual中出现了这个错误异常。 有什么想法吗？ 非常感谢。 对错误负责的代码是：

    private void doneActionPerformed(java.awt.event.ActionEvent evt)                {                                     
    // TODO add your handling code here:
    dispose();
    Menu m = new Menu(); //here is the error
    m.setVisible(true);
    }  

错误是：

    Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: test/Menu
at test.Step3.doneActionPerformed(Step3.java:115)
at test.Step3.access$000(Step3.java:13)
at test.Step3$1.actionPerformed(Step3.java:57)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
    at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

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你能用IDE运行任何代码吗，或者所有的代码都会引发这个异常？@HovercraftFullOfEels当我单击run时，它首先会显示三个windows类，当我单击按钮继续时，它会显示这个错误。请进一步解释。假设我们甚至不使用NetBeans，我们没有坐在您的屏幕前看到您所看到的。我们需要重要的细节。谢谢。@hoverofeels所以，我的程序运行没有问题。我关闭了netbeans，一个小时后又打开了。当我运行程序时，它显示了第一个窗口。我点击按钮继续，一切正常。下一个窗口也是如此。但当我单击按钮第三个窗口时，程序关闭，并显示此错误。然后，您需要向我们显示所涉及的代码、完整的错误消息，并指出哪一行是导致异常的原因。