Function<? super F, T> function, Supplier<F> supplier) {
    return new SupplierComposition<>(function, supplier);
  }

  private static final class SupplierComposition<
          F extends @Nullable Object, T extends @Nullable Object>
      implements Supplier<T>, Serializable {
    final Function<? super F, T> function;
    final Supplier<F> supplier;

    map.put("Null", null);
    Function<String, @Nullable Integer> function = Functions.forMap(map, 42);

    assertEquals(1, function.apply("One").intValue());
    assertEquals(42, function.apply("Two").intValue());
    assertEquals(3, function.apply("Three").intValue());
    assertNull(function.apply("Null"));

    new EqualsTester()
        .addEqualityGroup(function, Functions.forMap(map, 42))

          V extends @Nullable Object,
          M extends Multimap<K, V>>
      Collector<T, ?, M> toMultimap(
          java.util.function.Function<? super T, ? extends K> keyFunction,
          java.util.function.Function<? super T, ? extends V> valueFunction,
          java.util.function.Supplier<M> multimapSupplier) {
    return CollectCollectors.<T, K, V, M>toMultimap(keyFunction, valueFunction, multimapSupplier);
  }

  /**

import org.jspecify.annotations.Nullable;

/**
 * Legacy version of {@link java.util.function.Predicate java.util.function.Predicate}. Determines a
 * true or false value for a given input.
 *
 * <p>As this interface extends {@code java.util.function.Predicate}, an instance of this type may
 * be used as a {@code Predicate} directly. To use a {@code java.util.function.Predicate} where a

   * {@code function} to the argument, then evaluating using {@code this}. That is, for any pair of
   * non-null objects {@code x} and {@code y}, {@code equivalence.onResultOf(function).equivalent(a,
   * b)} is true if and only if {@code equivalence.equivalent(function.apply(a), function.apply(b))}
   * is true.
   *
   * <p>For example:
   *
   * {@snippet :

/**
 * Functional interface for boolean functions.
 * Represents a function that accepts one argument and produces a boolean result.
 * @param <T> the type of the input to the function
 */
@FunctionalInterface
public interface BooleanFunction<T> {
    /**
     * Applies this function to the given argument.
     * @param t the function argument
     * @return the function result
     */
    boolean apply(T t);

 *  @author Victor Jonsson, http://victorjonsson.se
 *  @license MIT
 */

 *  @author Victor Jonsson, http://victorjonsson.se
 *  @license MIT
 */

 *  @author Victor Jonsson, http://victorjonsson.se
 *  @license MIT
 */

 *  @author Victor Jonsson, http://victorjonsson.se
 *  @license MIT
 */