Verschluck doch NICHT die Exceptio, sondern gib zumindest den Stacktrace aus!
Meine Vermutung:
NPE weil ClassLoader.getSystemResource( "Hilfe.txt") null lieferte. Weitere Annäherung durch eigene Zeile dafür und teste mal mit "/Hilfe.txt" und die Datei muss im Root-Verzeichnis des Classpath liegen.
java.lang.NullPointerException
at WI.Wi_1$3.actionPerformed(Wi_1.java:155)
at javax.swing.AbstractButton.fireActionPerformed(UnknownSource)
at javax.swing.AbstractButton$Handler.actionPerformed(UnknownSource)
at javax.swing.DefaultButtonModel.fireActionPerformed(UnknownSource)
at javax.swing.DefaultButtonModel.setPressed(UnknownSource)
at javax.swing.AbstractButton.doClick(UnknownSource)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(UnknownSource)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(UnknownSource)
at java.awt.Component.processMouseEvent(UnknownSource)
at javax.swing.JComponent.processMouseEvent(UnknownSource)
at java.awt.Component.processEvent(UnknownSource)
at java.awt.Container.processEvent(UnknownSource)
at java.awt.Component.dispatchEventImpl(UnknownSource)
at java.awt.Container.dispatchEventImpl(UnknownSource)
at java.awt.Component.dispatchEvent(UnknownSource)
at java.awt.LightweightDispatcher.retargetMouseEvent(UnknownSource)
at java.awt.LightweightDispatcher.processMouseEvent(UnknownSource)
at java.awt.LightweightDispatcher.dispatchEvent(UnknownSource)
at java.awt.Container.dispatchEventImpl(UnknownSource)
at java.awt.Window.dispatchEventImpl(UnknownSource)
at java.awt.Component.dispatchEvent(UnknownSource)
at java.awt.EventQueue.dispatchEventImpl(UnknownSource)
at java.awt.EventQueue.access$000(UnknownSource)
at java.awt.EventQueue$3.run(UnknownSource)
at java.awt.EventQueue$3.run(UnknownSource)
at java.security.AccessController.doPrivileged(NativeMethod)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(UnknownSource)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(UnknownSource)
at java.awt.EventQueue$4.run(UnknownSource)
at java.awt.EventQueue$4.run(UnknownSource)
at java.security.AccessController.doPrivileged(NativeMethod)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(UnknownSource)
at java.awt.EventQueue.dispatchEvent(UnknownSource)
at java.awt.EventDispatchThread.pumpOneEventForFilters(UnknownSource)
at java.awt.EventDispatchThread.pumpEventsForFilter(UnknownSource)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(UnknownSource)
at java.awt.EventDispatchThread.pumpEvents(UnknownSource)
at java.awt.EventDispatchThread.pumpEvents(UnknownSource)
at java.awt.EventDispatchThread.run(UnknownSource)
Anscheinend ist irgendwas null, vermutlich findet er die Textdatei nicht. Entweder ist also der Desktop null, oder die Datei. Gib am besten mal beide aus, bevor du die Datei öffnest!