* 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>
 *

/**
 * 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>
 *

import java.util.stream.Collector;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Provides static methods for working with {@link Comparator} instances. For many other helpful
 * comparator utilities, see either {@code Comparator} itself (for Java 8+), or {@code
 * com.google.common.collect.Ordering} (otherwise).
 *
 * <h3>Relationship to {@code Ordering}</h3>
 *