code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC licenses this file
  // to you under the Apache License, Version 2.0 (the
  // "License"); you may not use this file except in compliance
  // with the License.  You may obtain a copy of the License at
  //
  //   http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing,
  // software distributed under the License is distributed on an
  // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  // KIND, either express or implied.  See the License for the
  // specific language governing permissions and limitations
  // under the License.
  
  package org.openqa.selenium.support.pagefactory;
  
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  import org.openqa.selenium.By;
  import org.openqa.selenium.NoSuchElementException;
  import org.openqa.selenium.SearchContext;
  import org.openqa.selenium.WebElement;
  
  /**
   * Mechanism used to locate elements within a document using a series of other lookups. This class
   * will find all DOM elements that matches each of the locators in sequence, e.g.
   *
   * <pre>
   * driver.findElements(new ByChained(by1, by2))
   * </pre>
   *
   * will find all elements that match <var>by2</var> and appear under an element that matches
   * <var>by1</var>.
   */
  public class ByChained extends By implements Serializable {
  
    private static final long serialVersionUID = 1563769051170172451L;
  
    private By[] bys;
  
    public ByChained(By... bys) {
      this.bys = bys;
    }
  
    @Override
    public WebElement findElement(SearchContext context) {
      List<WebElement> elements = findElements(context);
      if (elements.isEmpty())
        throw new NoSuchElementException("Cannot locate an element using " + toString());
      return elements.get(0);
    }
  
    @Override
    public List<WebElement> findElements(SearchContext context) {
      if (bys.length == 0) {
        return new ArrayList<>();
      }
  
      List<WebElement> elems = bys[0].findElements(context);
      for (int i = 1; i < bys.length; i++) {
        if (elems.isEmpty()) {
          break; // if any one of the bys finds no elements, then return no elements
        }
        final By by = bys[i];
        elems =
            elems.stream()
                .map(elem -> elem.findElements(by))
                .flatMap(List::stream)
                .collect(Collectors.toList());
      }
  
      return elems;
    }
  
    @Override
    public String toString() {
      return String.format(
          "By.chained({%s})", Stream.of(bys).map(By::toString).collect(Collectors.joining(",")));
    }
  }
  