FULL PRODUCT VERSION :
jre6u21, jre7u45

ADDITIONAL OS VERSION INFORMATION :
Windows XP,, Windows 8.1

EXTRA RELEVANT SYSTEM CONFIGURATION :
java access bridge must be enabled in accessibility.properties

A DESCRIPTION OF THE PROBLEM :
When java access bridge is enabled, the getTableCellRendererComponent is often called with a null reference to the object to render. Without java acccess bridge enabled, everything works fine.

ADDITIONAL REGRESSION INFORMATION:
jre7u45

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run IncellEditDemo.jar and select the JComboboxess in the second column. The stdout shows the parameter of the call to getTableCellRendererComponent and getTableCellEditorComponent.


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
RENDER: passed value is: "0: item 0", at: (0, 1); isSelected: false
RENDER: passed value is: "1: item 0", at: (1, 1); isSelected: false
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
RENDER: passed value is: "0: item 0", at: (0, 1); isSelected: false
RENDER: passed value is: "1: item 0", at: (1, 1); isSelected: false
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
EDIT: passed value is: "0: item 0", at: (0, 1); isSelected: false
RENDER: passed value is: "1: item 0", at: (1, 1); isSelected: false
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
RENDER: passed value is: "1: item 0", at: (1, 1); isSelected: false
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
EDIT: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "0: item 2", at: (0, 1); isSelected: false
RENDER: passed value is: "1: item 0", at: (1, 1); isSelected: false
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
EDIT: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
ACTUAL -
ENDER: passed value is: "0: item 0", at: (0, 1); isSelected: false
RENDER: passed value is: "1: item 0", at: (1, 1); isSelected: false
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
RENDER: passed value is: "0: item 0", at: (0, 1); isSelected: false
RENDER: passed value is: "1: item 0", at: (1, 1); isSelected: false
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
EDIT: passed value is: "0: item 0", at: (0, 1); isSelected: false
RENDER: passed value is: "null", at: (0, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "1: item 0", at: (1, 1); isSelected: false
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
RENDER: passed value is: "1: item 0", at: (1, 1); isSelected: false
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
EDIT: passed value is: "1: item 0", at: (1, 1); isSelected: false
RENDER: passed value is: "null", at: (0, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "null", at: (1, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "0: item 0", at: (0, 1); isSelected: false
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
EDIT: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "null", at: (1, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "null", at: (2, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "1: item 0", at: (1, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
EDIT: passed value is: "3: item 0", at: (3, 1); isSelected: false
RENDER: passed value is: "null", at: (2, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "null", at: (3, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "2: item 0", at: (2, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "6: item 0", at: (6, 1); isSelected: false
EDIT: passed value is: "4: item 0", at: (4, 1); isSelected: false
RENDER: passed value is: "null", at: (3, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "null", at: (4, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "3: item 0", at: (3, 1); isSelected: false
EDIT: passed value is: "5: item 0", at: (5, 1); isSelected: false
RENDER: passed value is: "null", at: (4, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "null", at: (5, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "4: item 0", at: (4, 1); isSelected: false
EDIT: passed value is: "6: item 0", at: (6, 1); isSelected: false
RENDER: passed value is: "null", at: (5, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "null", at: (6, 1); isSelected: false
RENDER: returning <null>
RENDER: passed value is: "5: item 0", at: (5, 1); isSelected: false

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package InCellEditDemo;

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import javax.accessibility.AccessibleContext;
import static javax.swing.BorderFactory.createTitledBorder;
import javax.swing.DefaultCellEditor;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JPanel;
import javax.swing.JFrame;
import javax.swing.JTable;
import javax.swing.SwingUtilities;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableColumn;

/**
 *
 */
public class InCellEditView extends JFrame
 implements ActionListener, WindowListener {

  /**
   *
   */
  @SuppressWarnings("LeakingThisInConstructor")
  public InCellEditView()
  {
    setTitle("Testapplikation In-Cell Edit in Tabellen");
    addWindowListener(this);
  }

  /**
   * Set accessibility info of context
   *
   * @param context
   * @param name
   * @param desc
   */
  private void _setAccessibilityInfo(AccessibleContext context,
   String name, String desc)
  {
    context.setAccessibleName(name);
    context.setAccessibleDescription(desc);
  }

  /**
   * Exit application
   *
   * @param e
   */
  private void _handleOKButton(ActionEvent e)
  {
    System.exit(0);
  }

  /**
   * Handle button action
   *
   * @param e
   */
  @Override
  public void actionPerformed(ActionEvent e)
  {
    String action = e.getActionCommand();
    switch (action) {
    case "Exit":
      _handleOKButton(e);
      break;
    default:
      break;
    }
  }

  /**
   *
   */
  private void _setupLayout()
  {
    JPanel panel = new JPanel(new GridBagLayout());

    JButton exitButton = new JButton("Exit");
    exitButton.addActionListener(this);
    _setAccessibilityInfo(exitButton.getAccessibleContext(), "Exit",
     "With this button you will leave the applikation");

    // Table view panel
    JPanel tableViewPanel = new JPanel(new BorderLayout());
    tableViewPanel.setBorder(createTitledBorder("Table view panel"));
    JTable t = _createTable();
    tableViewPanel.add(t.getTableHeader(), BorderLayout.PAGE_START);
    tableViewPanel.add(t, BorderLayout.CENTER);

    // Control panel
    JPanel controlPanel = new JPanel(new GridBagLayout());
    controlPanel.setBorder(createTitledBorder("Control panel"));

    GridBagConstraints c = new GridBagConstraints();
    c.gridy = 0;
    c.gridx = 0;
    c.gridwidth = 2;
    c.insets.top = 0;
    c.insets.left = 0;
    c.anchor = GridBagConstraints.CENTER;
    c.fill = GridBagConstraints.NONE;
    controlPanel.add(exitButton, c);

    // Layout panel
    c.insets.bottom = 0;
    c.insets.top = 0;
    c.insets.left = 0;
    c.insets.right = 0;
    c.gridx = 0;
    c.gridy = 0;
    c.anchor = GridBagConstraints.NORTHWEST;
    c.fill = GridBagConstraints.BOTH;
    c.weightx = 1.0;
    c.weighty = 1.0;
    panel.add(tableViewPanel, c);
    c.gridy++;
    panel.add(controlPanel, c);
    add(panel);
    pack();
  }

  public class MyTableModel extends DefaultTableModel {
    private static final int NUM_COLUMNS = 2;
    public int COL_ROWID = 0;
    public int COL_ENUM = 1;
    private final Object[][] _data;
    private final Object[] _headers;

    public MyTableModel(int rows)
    {
      super(rows, NUM_COLUMNS);

      _headers = new Object[NUM_COLUMNS];
      _headers[COL_ROWID] = "Row";
      _headers[COL_ENUM] = "Enum";
      setColumnIdentifiers(_headers);

      _data = new Object[NUM_COLUMNS][rows];
      for (int j = 0; j < rows; j++) {
        String[] items = new String[rows];

        for (int i = 0; i < rows; i++) {
          items[i] = (j + ": item " + i);
        }

        _data[0][j] = j;
        _data[COL_ENUM][j] = new JComboBox<>(items);
      }
    }

    @Override
    public Object getValueAt(int row, int col)
    {
      if ((row >= 0) && (row < getRowCount()) && (col >= 0) && (col
       < getColumnCount())) {
        if (col == COL_ENUM) {
          return ((JComboBox) _data[col][row]).getSelectedItem();
        }
        else {
          return _data[col][row];
        }
      }
      return null;
    }

    public Object getDataAt(int row, int col)
    {
      if ((row >= 0) && (row < getRowCount()) && (col >= 0) && (col
       < getColumnCount())) {
        return _data[col][row];
      }
      return null;
    }
  };

  public class MyComboRenderer extends DefaultTableCellRenderer {
    public MyComboRenderer()
    {
      super();
    }

    @Override
    public Component getTableCellRendererComponent(JTable table, Object value,
     boolean isSelected, boolean hasFocus, int row, int column)
    {
      System.out.println("RENDER: passed value is: \"" + value + "\", at: ("
       + row + ", " + column + "); isSelected: " + isSelected);

      if (value == null) {
        System.out.println("RENDER: returning <null>");
        return null;
      }
      return super.getTableCellRendererComponent(table, value, isSelected,
       hasFocus, row, column);
    }
  }

  public class MyComboEditor extends DefaultCellEditor {
    private final MyTableModel _m;

    public MyComboEditor(MyTableModel m)
    {
      super(new JComboBox());
      _m = m;
    }

    @Override
    public Component getTableCellEditorComponent(JTable table, Object value,
     boolean isSelected, int row, int column)
    {
      System.out.println("EDIT: passed value is: \"" + value + "\", at: (" + row
       + ", " + column + "); isSelected: " + isSelected);
      if (value == null) {
        System.out.println("EDIT: returning <null>");
        return null;
      }
      if (column == _m.COL_ENUM) {
        return (JComboBox) _m.getDataAt(row, column);
      }
      return super.getTableCellEditorComponent(table, value, isSelected,
       row, column);
    }
  };

  private JTable _createTable()
  {
    MyTableModel m = new MyTableModel(7);
    JTable table = new JTable(m) {
      @Override
      public boolean isCellEditable(int row, int column)
      {
        return column == ((MyTableModel) getModel()).COL_ENUM;
      }
    };
    TableColumn tc = table.getColumnModel().getColumn(m.COL_ENUM);

    tc.setPreferredWidth(70);
    tc.setCellRenderer(new MyComboRenderer());
    tc.setCellEditor(new MyComboEditor(m));

    table.setRowHeight(22);
    table.setAutoResizeMode(JTable.AUTO_RESIZE_ALL_COLUMNS);

    table.setShowGrid(true);

    return table;
  }

  @Override
  public void windowOpened(WindowEvent e)
  {
  }

  @Override
  public void windowClosing(WindowEvent e)
  {
    dispose();
  }

  @Override
  public void windowClosed(WindowEvent e)
  {
    System.exit(0);
  }

  @Override
  public void windowIconified(WindowEvent e)
  {
  }

  @Override
  public void windowDeiconified(WindowEvent e)
  {
  }

  @Override
  public void windowActivated(WindowEvent e)
  {
  }

  @Override
  public void windowDeactivated(WindowEvent e)
  {
  }

  /**
   *
   * @param args
   */
  public static void main(String[] args)
  {
    SwingUtilities.invokeLater(new Runnable() {
      @Override
      public void run()
      {
        InCellEditView view = new InCellEditView();
        view._setupLayout();
        view.setVisible(true);
      }
    });
  }
}

---------- END SOURCE ----------