Nós poderíamos fazer melhor.

Podemos declarar um modelo `UserBase` que serve como base para nossos outros modelos. E então podemos fazer subclasses desse modelo que herdam seus atributos (declarações de tipo, validação, etc.).

Toda conversão de dados, validação, documentação, etc. ainda funcionará normalmente.

    expectContents(asList(elements));
  }

  /**
   * Asserts that the collection under test contains exactly the given elements, respecting
   * cardinality but not order. Subclasses may override this method to provide stronger assertions,
   * e.g., to check ordering in lists, but realize that <strong>unless a test extends {@link

 *
 * @author Charles Fry
 * @since 10.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class AbstractCache<K, V> implements Cache<K, V> {

  /** Constructor for use by subclasses. */
  protected AbstractCache() {}

  /** @since 11.0 */
  @Override
  public V get(K key, Callable<? extends V> valueLoader) throws ExecutionException {
    throw new UnsupportedOperationException();
  }

import java.util.Set;
import junit.framework.TestCase;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests representing the contract of {@link Map}. Concrete subclasses of this base class test
 * conformance of concrete {@link Map} subclasses to that contract.
 *
 * @param <K> the type of keys used by the maps under test
 * @param <V> the type of mapped values used the maps under test
 * @author George van den Driessche
 */

/**
 * Helper classes for various benchmarks.
 *
 * @author Christopher Swenson
 */
final class BenchmarkHelpers {
  /** So far, this is the best way to test various implementations of {@link Set} subclasses. */
  public interface CollectionsImplEnum {
    <E extends Comparable<E>> Collection<E> create(Collection<E> contents);

    String name();
  }

  public interface MapsImplEnum {

     */
    Builder<K, V> makeBuilder(int size) {
      return new Builder<>(size);
    }

    private static final long serialVersionUID = 0;
  }

  /**
   * Returns a serializable form of this object. Non-public subclasses should not override this

  @ParametricNullness
  V checkValue(@ParametricNullness V value) {
    return value;
  }

  /**
   * Specifies the delegate maps going in each direction. Called by the constructor and by
   * subclasses during deserialization.
   */
  void setDelegates(Map<K, V> forward, Map<V, K> backward) {
    checkState(delegate == null);
    checkState(inverse == null);
    checkArgument(forward.isEmpty());

 * </ul>
 *
 * @since 14.0
 * @author Colin Decker
 */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public abstract class ByteSource {

  /** Constructor for use by subclasses. */
  protected ByteSource() {}

  /**
   * Returns a {@link CharSource} view of this byte source that decodes bytes read from this source
   * as characters using the given {@link Charset}.
   *

  /** Constructor for use by subclasses. */
  protected Converter() {
    this(true);
  }

  /** Constructor used only by {@code LegacyConverter} to suspend automatic null-handling. */
  Converter(boolean handleNullAutomatically) {
    this.handleNullAutomatically = handleNullAutomatically;
  }

  // SPI methods (what subclasses must implement)

  /**

 * Implementation of {@link ImmutableMap} used for 0 entries and for 2+ entries. Additional
 * implementations exist for particular cases, like {@link ImmutableTable} views and hash flooding.
 * (This doc discusses {@link ImmutableMap} subclasses only for the JRE flavor; the Android flavor
 * differs.)
 *
 * @author Jesse Wilson
 * @author Kevin Bourrillion
 * @author Gregory Kick
 */
@GwtCompatible(serializable = true, emulated = true)