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.internal;
  
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.function.Function;
  import java.util.stream.Stream;
  
  public class Either<A, B> implements Iterable<B> {
    private final A left;
    private final B right;
  
    private Either(A a, B b) {
      left = a;
      right = b;
    }
  
    public static <A, B> Either<A, B> left(A a) {
      return new Either<>(a, null);
    }
  
    public static <A, B> Either<A, B> right(B b) {
      return new Either<>(null, b);
    }
  
    public boolean isLeft() {
      return left != null;
    }
  
    public boolean isRight() {
      return right != null;
    }
  
    public A left() {
      return left;
    }
  
    public B right() {
      return right;
    }
  
    public <R> R map(Function<? super B, ? extends R> mapper) {
      Require.nonNull("Mapper", mapper);
      return mapper.apply(right());
    }
  
    public <R> R mapLeft(Function<? super A, ? extends R> mapper) {
      Require.nonNull("Mapper", mapper);
      return mapper.apply(left());
    }
  
    @Override
    public Iterator<B> iterator() {
      return Collections.singleton(right()).iterator();
    }
  
    public Stream<B> stream() {
      return Stream.of(right());
    }
  
    @Override
    public String toString() {
      return "[Either(" + (isLeft() ? "left" : "right") + "): " + (isLeft() ? left() : right()) + "]";
    }
  }
  