public @Nullable E floor(E e) {
    return delegate.floor(checkValid(e));
  }

  @Override
  public SortedSet<E> headSet(E toElement) {
    return headSet(toElement, false);
  }

  @Override
  public NavigableSet<E> headSet(E toElement, boolean inclusive) {
    return new SafeTreeSet<>(delegate.headSet(checkValid(toElement), inclusive));
  }

  @Override
  public @Nullable E higher(E e) {

  public @Nullable E floor(E e) {
    return delegate.floor(checkValid(e));
  }

  @Override
  public SortedSet<E> headSet(E toElement) {
    return headSet(toElement, false);
  }

  @Override
  public NavigableSet<E> headSet(E toElement, boolean inclusive) {
    return new SafeTreeSet<>(delegate.headSet(checkValid(toElement), inclusive));
  }

  @Override
  public @Nullable E higher(E e) {

          ((SortedSet<E>) unfiltered).subSet(fromElement, toElement), predicate);
    }

    @Override
    public SortedSet<E> headSet(@ParametricNullness E toElement) {
      return new FilteredSortedSet<>(((SortedSet<E>) unfiltered).headSet(toElement), predicate);
    }

    @Override
    public SortedSet<E> tailSet(@ParametricNullness E fromElement) {

    SortedSet<String> set = of("e", "f", "b", "d", "c");
    assertTrue(set.headSet("e") instanceof ImmutableSortedSet);
    assertThat(set.headSet("e")).containsExactly("b", "c", "d").inOrder();
    assertThat(set.headSet("g")).containsExactly("b", "c", "d", "e", "f").inOrder();
    assertThat(set.headSet("a")).isSameInstanceAs(this.<String>of());
    assertThat(set.headSet("b")).isSameInstanceAs(this.<String>of());
  }

  }

  public void testRowKeySetHeadSet() {
    sortedTable = create("foo", 1, 'a', "bar", 1, 'b', "foo", 3, 'c');
    Set<String> set = sortedTable.rowKeySet().headSet("cat");
    assertEquals(singleton("bar"), set);
    set.clear();
    assertTrue(set.isEmpty());
    assertEquals(singleton("foo"), sortedTable.rowKeySet());
  }

  public void testRowKeySetTailSet() {

    return forward.subSet(toElement, toInclusive, fromElement, fromInclusive).descendingSet();
  }

  @Override
  ImmutableSortedSet<E> tailSetImpl(E fromElement, boolean inclusive) {
    return forward.headSet(fromElement, inclusive).descendingSet();
  }

  @Override
  @GwtIncompatible // NavigableSet
  public ImmutableSortedSet<E> descendingSet() {
    return forward;
  }

  @Override

    assertThat(keySet.first()).isNull();
    assertThat(keySet.last()).isEqualTo("google");
    assertEquals(StringLength.COMPARATOR, keySet.comparator());
    assertEquals(Sets.<@Nullable String>newHashSet(null, "tree"), keySet.headSet("yahoo"));
    assertEquals(newHashSet("google"), keySet.tailSet("yahoo"));
    assertEquals(newHashSet("tree"), keySet.subSet("ask", "yahoo"));
  }

  @GwtIncompatible // SerializableTester

    assertThat(elementSet.first()).isEqualTo("a");
    assertThat(elementSet.last()).isEqualTo("c");
    assertEquals(Ordering.natural(), elementSet.comparator());

    assertThat(elementSet.headSet("b")).containsExactly("a");
    assertThat(elementSet.tailSet("b")).containsExactly("b", "c").inOrder();
    assertThat(elementSet.subSet("a", "c")).containsExactly("a", "b").inOrder();
  }

<%@page pageEncoding="UTF-8" contentType="text/html; charset=UTF-8"%>
<nav class="main-header navbar navbar-expand navbar-dark navbar-secondary">
	<ul class="navbar-nav">
		<li class="nav-item">
			<a class="nav-link" data-widget="pushmenu" href="#">
				<i class="fas fa-bars" aria-hidden="true"></i>
				<span class="sr-only"><la:message
						key="labels.admin_toggle_navi" /></span>
			</a>
		</li>
	</ul>
	<ul class="navbar-nav ml-auto">

# Header 參數 { #header-parameters }

你可以用與定義 `Query`、`Path`、`Cookie` 參數相同的方式來定義 Header 參數。

## 匯入 `Header` { #import-header }

先匯入 `Header`：

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[3] *}

## 宣告 `Header` 參數 { #declare-header-parameters }

接著使用與 `Path`、`Query`、`Cookie` 相同的結構來宣告標頭參數。

你可以設定預設值，以及所有額外的驗證或註解參數：

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[9] *}

/// note | 注意