@Test
    @DisplayName("ltime field is mutable")
    void testLtimeField() {
        TestLocking t = new TestLocking();

        // Initial value
        assertEquals(0L, t.ltime, "ltime should start at 0");

        // Set new value
        long currentTime = System.currentTimeMillis();
        t.ltime = currentTime;
        assertEquals(currentTime, t.ltime, "ltime should be mutable");
    }

    @Test

  public static <E extends Enum<E>> Collector<E, ?, ImmutableSet<E>> toImmutableEnumSet() {
    return CollectCollectors.toImmutableEnumSet();
  }

  /**
   * Returns a new, <i>mutable</i> {@code EnumSet} instance containing the given elements in their
   * natural order. This method behaves identically to {@link EnumSet#copyOf(Collection)}, but also
   * accepts non-{@code Collection} iterables and empty iterables.

 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public final class Lists {
  private Lists() {}

  // ArrayList

  /**
   * Creates a <i>mutable</i>, empty {@code ArrayList} instance.
   *
   * <p><b>Note:</b> if mutability is not required, use {@link ImmutableList#of()} instead.
   *

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * A mutable type-to-instance map. See also {@link ImmutableTypeToInstanceMap}.
 *
 * @author Ben Yu
 * @since 13.0
 */
public final class MutableTypeToInstanceMap<B extends @Nullable Object>

   * As such, this field must be cleared before every map mutation.
   *
   * Note about volatile: volatile doesn't make it safe to read from a mutable graph in one thread
   * while writing to it in another. All it does is help with _reading_ from multiple threads
   * concurrently. For more information, see AbstractNetworkTest.concurrentIteration.
   */

        if (subgraph.nodes().contains(successorNode)) {
          subgraph.addEdge(node, successorNode, edge);
        }
      }
    }
    return subgraph;
  }

  /** Creates a mutable copy of {@code graph} with the same nodes and edges. */
  public static <N> MutableGraph<N> copyOf(Graph<N> graph) {
    MutableGraph<N> copy = GraphBuilder.from(graph).expectedNodeCount(graph.nodes().size()).build();

        if (subgraph.nodes().contains(successorNode)) {
          subgraph.addEdge(node, successorNode, edge);
        }
      }
    }
    return subgraph;
  }

  /** Creates a mutable copy of {@code graph} with the same nodes and edges. */
  public static <N> MutableGraph<N> copyOf(Graph<N> graph) {
    MutableGraph<N> copy = GraphBuilder.from(graph).expectedNodeCount(graph.nodes().size()).build();

      AvlNode<E> newRoot = new AvlNode<>(element, occurrences);
      successor(header, newRoot, header);
      rootReference.checkAndSet(root, newRoot);
      return 0;
    }
    int[] result = new int[1]; // used as a mutable int reference to hold result
    AvlNode<E> newRoot = root.add(comparator(), element, occurrences, result);
    rootReference.checkAndSet(root, newRoot);
    return result[0];
  }

  @CanIgnoreReturnValue

 *   <li>Access and modify project properties</li>
 *   <li>Manage repository configurations</li>
 *   <li>Handle project forking states</li>
 * </ul>
 *
 * The service maintains the mutable state of projects as they progress through
 * their build lifecycle, ensuring thread-safety and proper state management.
 * All implementations must be thread-safe as they may be accessed concurrently
 * during parallel builds.

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * A mutable type-to-instance map. See also {@link ImmutableTypeToInstanceMap}.
 *
 * @author Ben Yu
 * @since 13.0
 */
public final class MutableTypeToInstanceMap<B extends @Nullable Object>