Java.lang.NullPointerException in JComponent

Question

hi below error i am getting, could you plz help me.
java.lang.NullPointerException
     at vobPrimCompare$1.getColumnClass(vobPrimCompare.java:170)
     at javax.swing.JTable.getColumnClass(JTable.java:1752)
     at javax.swing.JTable.getCellRenderer(JTable.java:3700)
     at javax.swing.plaf.basic.BasicTableUI.paintCell(BasicTableUI.java:1148)
     at javax.swing.plaf.basic.BasicTableUI.paintCells(BasicTableUI.java:1051)
     at javax.swing.plaf.basic.BasicTableUI.paint(BasicTableUI.java:974)
     at javax.swing.plaf.ComponentUI.update(ComponentUI.java:142)
     at javax.swing.JComponent.paintComponent(JComponent.java:541)
     at javax.swing.JComponent.paint(JComponent.java:808)
     at javax.swing.JComponent.paintChildren(JComponent.java:647)
     at javax.swing.JComponent.paint(JComponent.java:817)
     at javax.swing.JViewport.paint(JViewport.java:722)
     at javax.swing.JComponent.paintChildren(JComponent.java:647)
     at javax.swing.JComponent.paint(JComponent.java:817)
     at javax.swing.JComponent.paintChildren(JComponent.java:647)
     at javax.swing.JComponent.paint(JComponent.java:817)
     at javax.swing.JComponent.paintChildren(JComponent.java:647)
     at javax.swing.JComponent.paint(JComponent.java:817)
     at javax.swing.JComponent.paintWithOffscreenBuffer(JComponent.java:4787)
     at javax.swing.JComponent.paintDoubleBuffered(JComponent.java:4740)
     at javax.swing.JComponent._paintImmediately(JComponent.java:4685)
     at javax.swing.JComponent.paintImmediately(JComponent.java:4488)
     at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:410)
     at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:117)
     at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:189)
     at java.awt.EventQueue.dispatchEvent(EventQueue.java:478)
     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)what could be the problem, could u plz help me.
below code is for(vobPrimCompare.java)
public vobPrimCompare() {
    tm = new AbstractTableModel() {
      public int getColumnCount() { return headers.length; }
      public int getRowCount() { return( tabHash.size() ); }
      public boolean isCellEditable(int row, int col) {
          if (col==8) return true;
          return false;
      public String getColumnName(int col) { return headers[col]; }
      public Object getValueAt(int row, int col) {
        compareNode cell=(compareNode)tabHash.get(new Integer(row));
        if (cell == null) return "cell";
        if (col==8)
          if (cell.primUpdate) return "UPDATED"; else return "PASS";
        if (col==0) return cell.diffCode;
        if (tabHash==prodTabHash) return(getProdTabRow(cell, col));
        return(getDocTabRow(cell, col));
       public Class getColumnClass(int c) {
          return getValueAt(0, c).getClass();here last line is 170(at vobPrimCompare$1.getColumnClass(vobPrimCompare.java:170))

Answer 1

The value that's being returned is null, and then you're trying to call getClass on it, which is a nullpointerexception