* generator, builder, closure, or something else entirely. No guarantees are implied by this
 * interface.
 *
 * <p>The {@link Suppliers} class provides common suppliers and related utilities.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/FunctionalExplained">the use of functional types</a>.
 *
 * <h3>For Java 8+ users</h3>
 *

    multimap.put(null, 3);
    multimap.put(null, 1);
    multimap.put(null, 7);
    multimap.put("tree", 0);
    multimap.put("tree", null);
    return multimap;
  }

  /** Test that a TreeMultimap created from another uses the natural ordering. */
  public void testMultimapCreateFromTreeMultimap() {
    TreeMultimap<String, Integer> tree =
        TreeMultimap.create(StringLength.COMPARATOR, DECREASING_INT_COMPARATOR);

/**
 * Determines an output value based on an input value; a pre-Java-8 version of {@link
 * java.util.function.Function java.util.function.Function}.
 *
 * <p>The {@link Functions} class provides common functions and related utilities.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/FunctionalExplained">the use of {@code Function}</a>.
 *
 * <h3>For Java 8+ users</h3>
 *

    multimap.put(null, 3);
    multimap.put(null, 1);
    multimap.put(null, 7);
    multimap.put("tree", 0);
    multimap.put("tree", null);
    return multimap;
  }

  /** Test that a TreeMultimap created from another uses the natural ordering. */
  public void testMultimapCreateFromTreeMultimap() {
    TreeMultimap<String, Integer> tree =
        TreeMultimap.create(StringLength.COMPARATOR, DECREASING_INT_COMPARATOR);