import com.google.common.base.Function; import com.google.common.collect.FluentIterable; import javax.annotations.Nullable; import static com.google.common.collect.FluentIterable.from import java.util.ArrayList; import java.util.List; class A { void m(List<String> l) { Function<String, String> function = new Function<String, String>() { @Nullable @Override public String apply(@Nullable String x) { return x; } }; boolean strings = FluentIterable.from(l).transform(new Function<String, String>() { @Nullable @Override public String apply(@Nullable String x) { return x; } }).first().isPresent(); } }