replacement = "checkNotNull(ordering)",
      staticImports = "com.google.common.base.Preconditions.checkNotNull")
  @Deprecated
  public static <T extends @Nullable Object> Ordering<T> from(Ordering<T> ordering) {
    return checkNotNull(ordering);
  }

  /**
   * Returns an ordering that compares objects according to the order in which they appear in the

      replacement = "checkNotNull(ordering)",
      staticImports = "com.google.common.base.Preconditions.checkNotNull")
  @Deprecated
  public static <T extends @Nullable Object> Ordering<T> from(Ordering<T> ordering) {
    return checkNotNull(ordering);
  }

  /**
   * Returns an ordering that compares objects according to the order in which they appear in the

import org.jspecify.annotations.Nullable;

/** An ordering that treats {@code null} as less than all other values. */
@GwtCompatible
final class NullsFirstOrdering<T extends @Nullable Object> extends Ordering<@Nullable T>
    implements Serializable {
  final Ordering<? super T> ordering;

  NullsFirstOrdering(Ordering<? super T> ordering) {
    this.ordering = ordering;
  }

  @Override

import org.jspecify.annotations.Nullable;

/** An ordering that treats {@code null} as greater than all other values. */
@GwtCompatible
final class NullsLastOrdering<T extends @Nullable Object> extends Ordering<@Nullable T>
    implements Serializable {
  final Ordering<? super T> ordering;

  NullsLastOrdering(Ordering<? super T> ordering) {
    this.ordering = ordering;
  }

  @Override

import org.jspecify.annotations.Nullable;

/** An ordering that treats {@code null} as greater than all other values. */
@GwtCompatible
final class NullsLastOrdering<T extends @Nullable Object> extends Ordering<@Nullable T>
    implements Serializable {
  final Ordering<? super T> ordering;

  NullsLastOrdering(Ordering<? super T> ordering) {
    this.ordering = ordering;
  }

  @Override

    testComparator(arbitrary, list);
  }

  public void testUsingToString() {
    Ordering<Object> ordering = Ordering.usingToString();
    testComparator(ordering, 1, 12, 124, 2);
    assertThat(ordering.toString()).isEqualTo("Ordering.usingToString()");
    assertThat(reserialize(ordering)).isSameInstanceAs(ordering);
  }

  // use an enum to get easy serializability

    testComparator(arbitrary, list);
  }

  public void testUsingToString() {
    Ordering<Object> ordering = Ordering.usingToString();
    testComparator(ordering, 1, 12, 124, 2);
    assertThat(ordering.toString()).isEqualTo("Ordering.usingToString()");
    assertThat(reserialize(ordering)).isSameInstanceAs(ordering);
  }

  // use an enum to get easy serializability

    Ordering<@Nullable Comparable<?>> result = nullsLast;
    if (result == null) {
      result = nullsLast = super.<Comparable<?>>nullsLast();
    }
    return (Ordering<@Nullable S>) result;
  }

  @Override
  @SuppressWarnings("unchecked") // TODO(kevinb): the right way to explain this??
  public <S extends Comparable<?>> Ordering<S> reverse() {

import org.jspecify.annotations.Nullable;

/** An ordering that treats {@code null} as less than all other values. */
@GwtCompatible
final class NullsFirstOrdering<T extends @Nullable Object> extends Ordering<@Nullable T>
    implements Serializable {
  final Ordering<? super T> ordering;

  NullsFirstOrdering(Ordering<? super T> ordering) {
    this.ordering = ordering;
  }

  @Override

    Ordering<@Nullable Comparable<?>> result = nullsLast;
    if (result == null) {
      result = nullsLast = super.<Comparable<?>>nullsLast();
    }
    return (Ordering<@Nullable S>) result;
  }

  @Override
  @SuppressWarnings("unchecked") // TODO(kevinb): the right way to explain this??
  public <S extends Comparable<?>> Ordering<S> reverse() {