为什么我得到NoClassDefFoundError异常？

HIE所有我正在开发的DICOM浏览器当前的应用程序在NetBeans平台我开发的应用程序和使用dcm4che罐子API加载DICOM图像，并得到下面的异常错误PLZ指导我在哪里，我错了....为什么我得到NoClassDefFoundError异常？

 Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: org/apache/log4j/Logger 
at org.dcm4cheri.imageio.plugins.DcmImageReaderConf.<clinit>(DcmImageReaderConf.java:73) 
at org.dcm4cheri.imageio.plugins.DcmImageReaderSpi.<clinit>(DcmImageReaderSpi.java:79) 
at newone.Newone.openFile(Newone.java:193) 
at newone.Newone.actionPerformed(Newone.java:137) 
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:6504) 
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321) 
at java.awt.Component.processEvent(Component.java:6269) 
at java.awt.Container.processEvent(Container.java:2229) 
at java.awt.Component.dispatchEventImpl(Component.java:4860) 
at java.awt.Container.dispatchEventImpl(Container.java:2287) 
at java.awt.Component.dispatchEvent(Component.java:4686) 
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:2713) 
at java.awt.Component.dispatchEvent(Component.java:4686) 
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707) 
at java.awt.EventQueue.access$000(EventQueue.java:101) 
at java.awt.EventQueue$3.run(EventQueue.java:666) 
at java.awt.EventQueue$3.run(EventQueue.java:664) 
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:680) 
at java.awt.EventQueue$4.run(EventQueue.java:678) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76) 
at java.awt.EventQueue.dispatchEvent(EventQueue.java:677) 
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211) 
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128) 
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105) 
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90) 
    Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Logger 
at java.net.URLClassLoader$1.run(URLClassLoader.java:366) 
at java.net.URLClassLoader$1.run(URLClassLoader.java:355) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.net.URLClassLoader.findClass(URLClassLoader.java:354) 
at java.lang.ClassLoader.loadClass(ClassLoader.java:423) 
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308) 
at java.lang.ClassLoader.loadClass(ClassLoader.java:356) 
... 40 more 
    Exception in thread "Thread-3" java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 1 
at java.util.Vector.get(Vector.java:744) 
at newone.Newone.run(Newone.java:116) 
at java.lang.Thread.run(Thread.java:722) 
    Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: Array index out of range:    0 
at java.util.Vector.get(Vector.java:744) 
at newone.Newone.actionPerformed(Newone.java:162) 
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:6504) 
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321) 
at java.awt.Component.processEvent(Component.java:6269) 
at java.awt.Container.processEvent(Container.java:2229) 
at java.awt.Component.dispatchEventImpl(Component.java:4860) 
at java.awt.Container.dispatchEventImpl(Container.java:2287) 
at java.awt.Component.dispatchEvent(Component.java:4686) 
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:2713) 
at java.awt.Component.dispatchEvent(Component.java:4686) 
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707) 
at java.awt.EventQueue.access$000(EventQueue.java:101) 
at java.awt.EventQueue$3.run(EventQueue.java:666) 
at java.awt.EventQueue$3.run(EventQueue.java:664) 
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:680) 
at java.awt.EventQueue$4.run(EventQueue.java:678) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76) 
at java.awt.EventQueue.dispatchEvent(EventQueue.java:677) 
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211) 
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128) 
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105) 
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

来源

2012-05-07 PURAV PATEL

我们可以得到一些背景，以什么代码产生这个错误？你有没有把lib放在类路径中？通常，该错误意味着您忘记了包含库或其他资源。 –

你如何运行应用程序？什么是类路径？ –

@Jake +1更快:-) –