*     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
   *         .collect(toImmutableListMultimap(str -> str.charAt(0), str -> str.substring(1)));
   *
   * // is equivalent to
   *
   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
   *     new ImmutableListMultimap.Builder<Character, String>()
   *         .put('b', "anana")
   *         .putAll('a', "pple", "sparagus")

   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
   *         .collect(toImmutableListMultimap(str -> str.charAt(0), str -> str.substring(1)));
   *
   * // is equivalent to
   *
   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
   *     new ImmutableListMultimap.Builder<Character, String>()
   *         .put('b', "anana")
   *         .putAll('a', "pple", "sparagus")

   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
   *         .collect(toImmutableSetMultimap(str -> str.charAt(0), str -> str.substring(1)));
   *
   * // is equivalent to
   *
   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
   *     new ImmutableSetMultimap.Builder<Character, String>()
   *         .put('b', "anana")
   *         .putAll('a', "pple", "sparagus")

   *     Stream.of("banana", "apple", "carrot", "asparagus", "cherry")
   *         .collect(toImmutableSetMultimap(str -> str.charAt(0), str -> str.substring(1)));
   *
   * // is equivalent to
   *
   * static final Multimap<Character, String> FIRST_LETTER_MULTIMAP =
   *     new ImmutableSetMultimap.Builder<Character, String>()
   *         .put('b', "anana")
   *         .putAll('a', "pple", "sparagus")

   *
   * static {
   *     FIRST_LETTER_MULTIMAP = MultimapBuilder.treeKeys().arrayListValues().build();
   *     FIRST_LETTER_MULTIMAP.put('b', "anana");
   *     FIRST_LETTER_MULTIMAP.put('a', "pple");
   *     FIRST_LETTER_MULTIMAP.put('a', "sparagus");
   *     FIRST_LETTER_MULTIMAP.put('c', "arrot");
   *     FIRST_LETTER_MULTIMAP.put('c', "herry");
   * }
   * }
   *

   *
   * static {
   *     FIRST_LETTER_MULTIMAP = MultimapBuilder.treeKeys().arrayListValues().build();
   *     FIRST_LETTER_MULTIMAP.put('b', "anana");
   *     FIRST_LETTER_MULTIMAP.put('a', "pple");
   *     FIRST_LETTER_MULTIMAP.put('a', "sparagus");
   *     FIRST_LETTER_MULTIMAP.put('c', "arrot");
   *     FIRST_LETTER_MULTIMAP.put('c', "herry");
   * }
   * }
   *

Mas primeiro, vamos verificar alguns pequenos conceitos.

## Está com pressa?

Se você não se importa com qualquer um desses termos e só precisa adicionar segurança com autenticação baseada em usuário e senha _agora_, pule para os próximos capítulos.

## OAuth2

OAuth2 é uma especificação que define várias formas para lidar com autenticação e autorização.

Ela é bastante extensiva na especificação e cobre casos de uso muito complexos.

    }

    @Test
    @DisplayName("Should join with multi-character delimiter")
    void testJoinWithMultiCharDelimiter() {
        String result = StringUtil.join(" - ", "apple", "banana", "cherry");
        assertEquals("apple - banana - cherry", result);
    }

    @Test
    @DisplayName("Should handle null delimiter by inserting 'null' string")
    void testJoinWithNullDelimiter() {

                // Return unsorted list to test sorting
                return List.of("Zebra", "Apple", "Banana").stream().sorted().collect(java.util.stream.Collectors.toList());
            }
        };

        List<String> names = testFactory.loadDataStoreNameList();
        assertEquals(3, names.size());
        assertEquals("Apple", names.get(0));
        assertEquals("Banana", names.get(1));

## Common Use Cases

### E-commerce Search

```java
// Product search suggestions
SuggestItem product = new SuggestItem(
    new String[]{"iPhone 15 Pro", "Apple iPhone 15 Pro"},
    new String[][]{{"iphone"}, {"apple", "phone"}},
    1.5f,                               // boost popular products
    new String[]{"electronics", "mobile"},
    new String[]{"customer"},
    SuggestItem.Kind.DOCUMENT
);