contributions from many people at Google, as well as:

1ndig0, 372046933, abhinav, afzpatel, Akhil Goel, Alain Carlucci, Aleksei, Alen Huang, Alex, Amrinfathima-Mcw, Aravindh Balaji, Armand Picard, Aseem Athale, Ashiq Imran, Assoap, Chao, Chase Riley Roberts, Chenhao Jiang, chunhsue, chuntl, Chunyu Jin, Corentin Kerisit, Crefeda Rodrigues, dependabot[bot], Dragan Mladjenovic, Elen Kalda, Felix Thomasmathibalan, gabeweisz, Gauri Deshpande, Georg Stefan Schmid, Guozhong Zhuang, Harsha H S, Harshith_N, Hugo...

import org.jspecify.annotations.Nullable;

/**
 * A series of tests that support asserting that collections cannot be modified, either through
 * direct or indirect means.
 *
 * @author Robert Konigsberg
 */
@GwtCompatible
@NullMarked
public class UnmodifiableCollectionTests {

  public static void assertMapEntryIsUnmodifiable(Entry<?, ?> entry) {
    try {

 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/CollectionUtilitiesExplained#multimaps">{@code
 * Multimaps}</a>.
 *
 * @author Jared Levy
 * @author Robert Konigsberg
 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public final class Multimaps {
  private Multimaps() {}

  /**

 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/CollectionUtilitiesExplained#multimaps">{@code
 * Multimaps}</a>.
 *
 * @author Jared Levy
 * @author Robert Konigsberg
 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public final class Multimaps {
  private Multimaps() {}

  /**