forking Guava yourself.


        We want to see that new features have some significant advantage over the alternatives.
        These advantages can take
        [many forms](https://github.com/google/guava/wiki/PhilosophyExplained#utility), but taking
        the time to discuss them in detail will make it much clearer why this feature should be
        added to Guava.

  public void testPutNullValue_supported() {
    int size = getNumElements();

    multimap().put(k3(), null);

    assertGet(k3(), Lists.newArrayList((V) null)); // ImmutableList.of can't take null.
    assertEquals(size + 1, multimap().size());
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  public void testPutNullValue_unsupported() {
    try {

 *
 * <p>If the precondition is not met, the {@code Preconditions} method throws an unchecked exception
 * of a specified type, which helps the method in which the exception was thrown communicate that
 * its caller has made a mistake. This allows constructs such as
 *
 * <pre>{@code
 * public static double sqrt(double value) {
 *   if (value < 0) {
 *     throw new IllegalArgumentException("input is negative: " + value);
 *   }

      }
    }
    return args;
  }

  private <T> @Nullable T getDefaultValue(TypeToken<T> type) {
    // We assume that all defaults are generics-safe, even if they aren't,
    // we take the risk.
    @SuppressWarnings("unchecked")
    T defaultValue = (T) defaults.getInstance(type.getRawType());
    if (defaultValue != null) {
      return defaultValue;
    }

import javax.annotation.CheckForNull;

/**
 * An immutable well-formed internet domain name, such as {@code com} or {@code foo.co.uk}. Only
 * syntactic analysis is performed; no DNS lookups or other network interactions take place. Thus
 * there is no guarantee that the domain actually exists on the internet.
 *
 * <p>One common use of this class is to determine whether a given string is likely to represent an

    // The Dolphin algorithm is attractive because it does the fewest array reads and writes: each
    // array slot is read and written exactly once. However, it can have very poor memory locality:
    // benchmarking shows it can take 7 times longer than the other two in some cases. The other two
    // do n swaps, minus a delta (0 or 2 for Reversal, gcd(d, n) for Successive), so that's about

    }

    @Override
    public String toString() {
      return "Ordering.arbitrary()";
    }

    /*
     * We need to be able to mock identityHashCode() calls for tests, because it
     * can take 1-10 seconds to find colliding objects. Mocking frameworks that
     * can do magic to mock static method calls still can't do so for a system
     * class, so we need the indirection. In production, Hotspot should still

    ImmutableSet.Builder<ImmutableList<Class<?>>> allOverloads = ImmutableSet.builder();
    // The first two are for the overloads that don't take formatting args, e.g.
    // checkArgument(boolean) and checkArgument(boolean, Object)
    allOverloads.add(ImmutableList.<Class<?>>of(predicateType));
    allOverloads.add(ImmutableList.<Class<?>>of(predicateType, Object.class));

    }
  }

  /**
   * Returns {@code n} choose {@code k}, also known as the binomial coefficient of {@code n} and
   * {@code k}, that is, {@code n! / (k! (n - k)!)}.
   *
   * <p><b>Warning:</b> the result can take as much as <i>O(k log n)</i> space.
   *
   * @throws IllegalArgumentException if {@code n < 0}, {@code k < 0}, or {@code k > n}
   */
  public static BigInteger binomial(int n, int k) {
    checkNonNegative("n", n);

@GwtCompatible
@ElementTypesAreNonnullByDefault
/*
 * 1. The type parameter is <T> rather than <T extends @Nullable> so that we can use T in the
 * doForward and doBackward methods to indicate that the parameter cannot be null. (We also take
 * advantage of that for convertAll, as discussed on that method.)
 *
 * 2. The supertype of this class could be `Function<@Nullable A, @Nullable B>`, since