*       the same.
   *   <li>The special characters ".", "-", "*", and "_" remain the same.
   *   <li>The space character " " is converted into a plus sign "+".
   *   <li>All other characters are converted into one or more bytes using UTF-8 encoding and each
   *       byte is then represented by the 3-character string "%XY", where "XY" is the two-digit,
   *       uppercase, hexadecimal representation of the byte value.
   * </ul>
   *

    Iterator<String> iterator = asList("one", "two").iterator();
    IllegalArgumentException expected =
        assertThrows(IllegalArgumentException.class, () -> getOnlyElement(iterator));
    assertThat(expected).hasMessageThat().isEqualTo("expected one element but was: <one, two>");
  }

  public void testGetOnlyElement_noDefault_fiveElements() {
    Iterator<String> iterator = asList("one", "two", "three", "four", "five").iterator();

In the next sections you will see other options, configurations, and additional features.

/// tip

The next sections are **not necessarily "advanced"**.

And it's possible that for your use case, the solution is in one of them.

///

## Read the Tutorial first { #read-the-tutorial-first }

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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
 *

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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
 *

 *    prefix at all (`publicobject.com`). For most applications this is the best way to configure
 *    certificate pinning.
 *
 *  * **Exactly one subdomain**: Use a single asterisk like `*.publicobject.com` to match exactly
 *    one prefix (`www.publicobject.com`, `api.publicobject.com`). Be careful with this approach as
 *    no pinning will be enforced if additional prefixes are present, or if no prefixes are present.

And it can also be used by yourself, to debug, check and test the same application.

## The `password` flow { #the-password-flow }

Now let's go back a bit and understand what is all that.

The `password` "flow" is one of the ways ("flows") defined in OAuth2, to handle security and authentication.

OAuth2 was designed so that the backend or API could be independent of the server that authenticates the user.

# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF 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

 *   <dt>{@link Multiset}
 *   <dd>An extension of {@link java.util.Collection} that may contain duplicate values like a
 *       {@link java.util.List}, yet has order-independent equality like a {@link java.util.Set}.
 *       One typical use for a multiset is to represent a histogram.
 *   <dt>{@link ClassToInstanceMap}
 *   <dd>An extension of {@link java.util.Map} that associates a raw type with an instance of that
 *       type.
 * </dl>
 *

 *   <dt>{@link Multiset}
 *   <dd>An extension of {@link java.util.Collection} that may contain duplicate values like a
 *       {@link java.util.List}, yet has order-independent equality like a {@link java.util.Set}.
 *       One typical use for a multiset is to represent a histogram.
 *   <dt>{@link ClassToInstanceMap}
 *   <dd>An extension of {@link java.util.Map} that associates a raw type with an instance of that
 *       type.
 * </dl>
 *