How to use com.google.gwt.cell.client

 public abstract class GridStringColumn<M> extends Column<VwGovernorRule, String> {

  private String  text_;
  private String  tooltip_;
  private boolean defaultShown_ = true;
  private boolean hidden_       = false;

  public GridStringColumn(String fieldName, String text, String tooltip, boolean defaultShown, boolean sortable, boolean hidden) {
    super(new TextCell());
    setDataStoreName(fieldName);
    this.text_ = text;
    this.tooltip_ = tooltip;
    this.defaultShown_ = defaultShown;
    setSortable(sortable);
    this.hidden_ = hidden;
  }
}

@Override
public boolean isEditing(Context context, Element parent, String value) {
 ViewData viewData = getViewData(context.getKey());
 return viewData == null ? false : viewData.isEditing();
}

 @Override
 public void update(X value) {
  fieldUpdater.update(context.getIndex(), object, value);
  if (valueUpdater != null) {
   valueUpdater.update(object);
  }
 }
};

public void render(Context context, C value, SafeHtmlBuilder sb) {
 SafeHtmlBuilder cellBuilder = new SafeHtmlBuilder();
 cell.render(context, value, cellBuilder);
 sb.append(template.outerDiv(outerDivPadding, isIconUsed(value) ? getIconHtml(value)
   : placeHolderHtml, cellBuilder.toSafeHtml()));
}

 private <X> void setValueImpl(Context context, Element cellParent, C object,
   HasCell<C, X> hasCell) {
  hasCell.getCell().setValue(context, cellParent, hasCell.getValue(object));
 }  
}

private <X> boolean isEditingImpl(Context context, Element cellParent, C object,
  HasCell<C, X> hasCell) {
 return hasCell.getCell().isEditing(context, cellParent, hasCell.getValue(object));
}  

private <C> boolean resetFocusOnCellImpl(Context context, T value, HasCell<T, C> column,
  Element cellParent) {
 C cellValue = column.getValue(value);
 Cell<C> cell = column.getCell();
 return cell.resetFocus(context, cellParent, cellValue);
}

public void onBrowserEvent(Context context, Element parent, C value,
  NativeEvent event, ValueUpdater<C> valueUpdater) {
 cell.onBrowserEvent(context, getCellParent(parent), value, event,
   valueUpdater);
}

public void setValue(Context context, Element parent, C value) {
 cell.setValue(context, getCellParent(parent), value);
}

/**
 * Create the context for a column based on the current table building state.
 * 
 * @param column the column id
 * @return the context that contains the column index, row/subrow indexes, and the row value key
 */
public final Context createContext(int column) {
 return new Context(rowIndex, column, rowValueKey, subrowIndex);
}

 @Override
 public void update(C value) {
  fieldUpdater.update(index, rowValue, value);
 }
};

@Override
public void render(Context context, C value, SafeHtmlBuilder sb) {
 for (HasCell<C, ?> hasCell : hasCells) {
  render(context, value, sb, hasCell);
 }
}

 @Override
 protected void onEnterKeyDown(Context context, Element parent, C value,
   NativeEvent event, ValueUpdater<C> valueUpdater) {
  delegate.execute(value);
 }
}

/**
 * The wrapper around the image vertically aligned to the bottom.
 */
@Template("<div style=\"{0}position:absolute;bottom:0px;line-height:0px;\">{1}</div>")
SafeHtml imageWrapperBottom(SafeStyles styles, SafeHtml image);

/**
 * Construct a new {@link AbstractInputCell} with the specified consumed
 * events.
 * 
 * @param consumedEvents the events that this cell consumes
 */
public AbstractInputCell(String... consumedEvents) {
 super(getConsumedEventsImpl(consumedEvents));
}

  CellList<String> cl = new CellList<String>(new TextCell());
  CellList<String> cl = new CellList<String>(new TextCell());
  CellList<String> cl = new CellList<String>(new TextCell());
    return "%" + object + "%";
}, new Header<String>(new TextCell()) {

private <X> boolean resetFocusImpl(Context context, Element cellParent,
  C value, HasCell<C, X> hasCell) {
 X cellValue = hasCell.getValue(value);
 return hasCell.getCell().resetFocus(context, cellParent, cellValue);
}

 @Override
 public void update(C value) {
  fieldUpdater.update(index, object, value);
 }
};

/**
 * The wrapper around the image vertically aligned to the middle.
 */
@Template("<div style=\"{0}position:absolute;top:50%;line-height:0px;\">{1}</div>")
SafeHtml imageWrapperMiddle(SafeStyles styles, SafeHtml image);

/**
 * Construct a new TextHeader.
 *
 * @param text the header text as a String
 */
public TextHeader(String text) {
 super(new TextCell());
 this.text = text;
}