*       C}, instance methods are skipped for nulls test.
   *   <li>Nulls test is not performed on method return values unless the method is a visible static
   *       factory method whose return type is {@code C} or {@code C}'s subtype.
   * </ul>
   *
   * <p>In all cases, if {@code C} needs custom logic for testing nulls, you can add an explicit

       * we're copying into a `contents` array whose type allows it to contain nulls. Still, it's
       * worth noting that we promise not to put nulls into the array in the first `size` elements.
       * We uphold that promise here because our callers promise that `elements` will not contain
       * nulls in its first `n` elements.
       */
      System.arraycopy(elements, 0, contents, size, n);
      size += n;

   *       C}, instance methods are skipped for nulls test.
   *   <li>Nulls test is not performed on method return values unless the method is a visible static
   *       factory method whose return type is {@code C} or {@code C}'s subtype.
   * </ul>
   *
   * <p>In all cases, if {@code C} needs custom logic for testing nulls, you can add an explicit

import com.google.common.annotations.J2ktIncompatible;
import java.io.Serializable;
import java.util.List;
import org.jspecify.annotations.Nullable;

/**
 * An ordering that treats all references as equals, even nulls.
 *
 * @author Emily Soldal
 */
@GwtCompatible
final class AllEqualOrdering extends Ordering<@Nullable Object> implements Serializable {
  static final AllEqualOrdering INSTANCE = new AllEqualOrdering();

       * we're copying into a `contents` array whose type allows it to contain nulls. Still, it's
       * worth noting that we promise not to put nulls into the array in the first `size` elements.
       * We uphold that promise here because our callers promise that `elements` will not contain
       * nulls in its first `n` elements.
       */
      System.arraycopy(elements, 0, contents, size, n);
      size += n;

  }

  /*
   * All the ContiguousSet generators below manually reject nulls here. In principle, we'd like to
   * defer that to Range, since it's ContiguousSet.create() that's used to create the sets. However,
   * that gets messy here, and we already have null tests for Range.
   */

  /*
   * These generators also rely on consecutive integer inputs (not necessarily in order, but no

  /**
   * Visits the given types. Null types are ignored. This allows subclasses to call {@code
   * visit(parameterizedType.getOwnerType())} safely without having to check nulls.
   */
  public final void visit(@Nullable Type... types) {
    for (Type type : types) {
      if (type == null || !visited.add(type)) {
        // null owner type, or already visited;
        continue;
      }

    assertTrue("add(null) should return true", collection.add(null));
    expectAdded((E) null);
  }

  @CollectionFeature.Require(value = SUPPORTS_ADD, absent = ALLOWS_NULL_VALUES)
  public void testAdd_nullUnsupported() {
    assertThrows(NullPointerException.class, () -> collection.add(null));
    expectUnchanged();
    expectNullMissingWhenNullUnsupported("Should not contain null after unsupported add(null)");
  }

    assertTrue("add(null) should return true", collection.add(null));
    expectAdded((E) null);
  }

  @CollectionFeature.Require(value = SUPPORTS_ADD, absent = ALLOWS_NULL_VALUES)
  public void testAdd_nullUnsupported() {
    assertThrows(NullPointerException.class, () -> collection.add(null));
    expectUnchanged();
    expectNullMissingWhenNullUnsupported("Should not contain null after unsupported add(null)");
  }

  @Override
  public boolean contains(@Nullable Object target) {
    @Nullable Object[] table = this.table;
    if (target == null || table.length == 0) {
      return false;
    }
    for (int i = Hashing.smearedHash(target); ; i++) {
      i &= mask;
      Object candidate = table[i];
      if (candidate == null) {
        return false;
      } else if (candidate.equals(target)) {
        return true;
      }
    }
  }