六分铝塑管多少钱一米:java.lang.NullPointerException

jbuilder2005下编写的客户端界面显示不出来
出现下列：请问怎么解决？

java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(ImageIcon.java:138)
at chatroomclient.FrameClient.jbInit(FrameClient.java:127)
at chatroomclient.FrameClient.<init>(FrameClient.java:110)
at chatroomclient.Listener.<init>(Listener.java:48)
at chatroomclient.LoginFrame.jButtonLogin_actionPerformed(LoginFrame.java:115)
at chatroomclient.LoginFrame_jButtonLogin_actionAdapter.actionPerformed(LoginFrame.java:171)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1786)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(AbstractButton.java:1839)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:245)
at java.awt.Component.processMouseEvent(Component.java:5100)
at java.awt.Component.processEvent(Component.java:4897)
at java.awt.Container.processEvent(Container.java:1569)
at java.awt.Component.dispatchEventImpl(Component.java:3615)
at java.awt.Container.dispatchEventImpl(Container.java:1627)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3483)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3198)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3128)
at java.awt.Container.dispatchEventImpl(Container.java:1613)
at java.awt.Window.dispatchEventImpl(Window.java:1606)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:456)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)
public ImageIcon (URL location) {
this(location, location.toExternalForm());

第138行是这样的，ImageIcon.java不是我自己写的阿.