this.value = checkNotNull(value);
    }

    @Override
    public String toString() {
      return "value=" + value;
    }
  }

  @SuppressWarnings("ComparableType")
  private static class ComparableSubClass extends NonComparableSuperClass
      implements Comparable<NonComparableSuperClass> {

    ComparableSubClass(Integer value) {
      super(value);
    }

 * types, though their use may still require an explicit type parameter and/or warning suppression.
 *
 * @author Kevin Bourrillion
 */
@SuppressWarnings({"ComparableType", "rawtypes"}) // https://github.com/google/guava/issues/989
@GwtCompatible
@NullMarked
class LegacyComparable implements Comparable, Serializable {
  static final LegacyComparable X = new LegacyComparable("x");

  }

  // Compare by toString() to satisfy 2 properties:
  // 1. compareTo(null) should throw NullPointerException
  // 2. the order is deterministic and easy to understand, for debugging purpose.
  @SuppressWarnings("ComparableType")
  private static final class ByToString implements Comparable<Object>, Serializable {
    private static final ByToString INSTANCE = new ByToString();

    @Override
    public int compareTo(Object o) {

  }

  // Compare by toString() to satisfy 2 properties:
  // 1. compareTo(null) should throw NullPointerException
  // 2. the order is deterministic and easy to understand, for debugging purpose.
  @SuppressWarnings("ComparableType")
  private static final class ByToString implements Comparable<Object>, Serializable {
    private static final ByToString INSTANCE = new ByToString();

    @Override
    public int compareTo(Object o) {