java.lang.IllegalArgumentException: Comparison method violates its general contract!
   at java.util.ComparableTimSort.mergeLo(ComparableTimSort.java:744)
   at java.util.ComparableTimSort.mergeAt(ComparableTimSort.java:481)
   at java.util.ComparableTimSort.mergeCollapse(ComparableTimSort.java:406)
   at java.util.ComparableTimSort.sort(ComparableTimSort.java:213)
   at java.util.Arrays.sort(Arrays.java:1246)
   at javax.swing.DefaultRowSorter.sortExistingData(DefaultRowSorter.java:553)
   at javax.swing.DefaultRowSorter.setSortKeys(DefaultRowSorter.java:321)
   at javax.swing.DefaultRowSorter.toggleSortOrder(DefaultRowSorter.java:480)
   at javax.swing.plaf.basic.BasicTableHeaderUI$MouseInputHandler.mouseClicked(BasicTableHeaderUI.java:112)
   at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:270)
   at java.awt.Component.processMouseEvent(Component.java:6536)
   at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
   at java.awt.Component.processEvent(Component.java:6298)
   at java.awt.Container.processEvent(Container.java:2236)
   at java.awt.Component.dispatchEventImpl(Component.java:4889)
   at java.awt.Container.dispatchEventImpl(Container.java:2294)
   at java.awt.Component.dispatchEvent(Component.java:4711)
   at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4888)
   at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:4534)
   at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4466)
   at java.awt.Container.dispatchEventImpl(Container.java:2280)
   at java.awt.Window.dispatchEventImpl(Window.java:2746)
   at java.awt.Component.dispatchEvent(Component.java:4711)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
   at java.awt.EventQueue.access$500(EventQueue.java:97)
   at java.awt.EventQueue$3.run(EventQueue.java:709)
   at java.awt.EventQueue$3.run(EventQueue.java:703)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
   at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
   at java.awt.EventQueue$4.run(EventQueue.java:731)
   at java.awt.EventQueue$4.run(EventQueue.java:729)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:159)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)