GWT Celltable and Checkbox Column

// you need a selection model
private final MultiSelectionModel<usermodel> selectionModel = new MultiSelectionModel<usermodel>(operatorKeyProvider);

// you need a selection manager
private final DefaultSelectionEventManager<usermodel> selectionManager = DefaultSelectionEventManager.createCheckboxManager();

// you need the table ;)
@UiField CellTable<usermodel> table;

// then ...
selectionModel.addSelectionChangeHandler(
new SelectionChangeEvent.Handler() {
public void onSelectionChange(SelectionChangeEvent event) {
StringBuilder sb = new StringBuilder();
boolean first = true;
List&lt;UserModel&gt; selected = new ArrayList&lt;UserModel&gt;(selectionModel.getSelectedSet());

Collections.sort(selected);
for (UserModel value : selected) {
if (first) {
first = false;
} else {
sb.append(&quot;, &quot;);
}
sb.append(value.getFirstName());
}
}
});

table.setSelectionModel(selectionModel, selectionManager);

// create your column
Column<UserModel, Boolean> checkBoxColumn = new Column<UserModel, Boolean>(new CheckboxCell()) {

   @Override
   public Boolean getValue(UserModel object) {
    return selectionModel.isSelected(object);
   }
   
   @Override
   public FieldUpdater<UserModel, Boolean> getFieldUpdater() {
       return null;
      } 
   
  };