DataProvider { @SuppressWarnings("unchecked") public FilterValue<T> getFilter(String name) { return filterValues.getOrDefault(name, FilterValue.EMPTY); } DataProvider(Function<T, String> identifier, boolean multiSelect);   DataProvider(Function<T, String> identifier, boolean multiSelect, int pageSize); void update(Iterable<T> items); boolean contains(T item); boolean isVisible(T item); String getId(T item); Iterable<T> getAllItems(); Iterable<T> getFilteredItems(); Iterable<T> getVisibleItems(); void onSelect(SelectHandler<T> selectHandler); void selectAll(); void selectVisible(); void clearAllSelection(); void clearVisibleSelection(); void select(T item, boolean select); SelectionInfo<T> getSelectionInfo(); void addFilter(String name, FilterValue<T> filter); void removeFilter(String name); void clearFilters(); @SuppressWarnings("unchecked") FilterValue<T> getFilter(String name); boolean hasFilters(); void setComparator(Comparator<T> comparator); Comparator<T> getComparator(); void setPageSize(int pageSize); void gotoFirstPage(); void gotoPreviousPage(); void gotoNextPage(); void gotoLastPage(); void gotoPage(int page); PageInfo getPageInfo(); void addDisplay(Display<T> display);  }
@Test public void getFilter() throws Exception { assertFalse(single.hasFilters()); assertSame(FilterValue.EMPTY, single.getFilter("foo")); }