public interface PeekingIterator<E extends @Nullable Object> extends Iterator<E> {
  /**
   * Returns the next element in the iteration, without advancing the iteration.
   *
   * <p>Calls to {@code peek()} should not change the state of the iteration, except that it
   * <i>may</i> prevent removal of the most recent element via {@link #remove()}.
   *
   * @throws NoSuchElementException if the iteration has no more elements according to {@link
   *     #hasNext()}

    this.e4 = e4;
  }

  @Override
  public Iterator<E> iterator() {
    return asList().iterator();
  }

  public List<E> asList() {
    return Arrays.asList(e0(), e1(), e2(), e3(), e4());
  }

  public static class Strings extends SampleElements<String> {
    public Strings() {
      // elements aren't sorted, to better test SortedSet iteration ordering
      super("b", "a", "c", "d", "e");
    }

 * }
 * </pre>
 * <p>
 * By default, the {@link Object} class is also included in the iteration. If you do not want to include {@link Object},
 * specify {@literal false} for the second argument of {@link #iterable(Class, boolean)} or {@link #ClassIterator(Class, boolean)}.
 * </p>
 *
 * @author koichik
 */
public class ClassIterator implements Iterator<Class<?>> {

    /** The class */
    protected Class<?> clazz;

 * {@link #computeNext} method, and invoke the {@link #endOfData} method when appropriate.
 *
 * <p>Another example is an iterator that skips over null elements in a backing iterator. This could
 * be implemented as:
 *
 * {@snippet :
 * public static Iterator<String> skipNulls(final Iterator<String> in) {
 *   return new AbstractIterator<String>() {
 *     protected String computeNext() {
 *       while (in.hasNext()) {

public interface PeekingIterator<E extends @Nullable Object> extends Iterator<E> {
  /**
   * Returns the next element in the iteration, without advancing the iteration.
   *
   * <p>Calls to {@code peek()} should not change the state of the iteration, except that it
   * <i>may</i> prevent removal of the most recent element via {@link #remove()}.
   *
   * @throws NoSuchElementException if the iteration has no more elements according to {@link
   *     #hasNext()}

    this.e4 = e4;
  }

  @Override
  public Iterator<E> iterator() {
    return asList().iterator();
  }

  public List<E> asList() {
    return Arrays.asList(e0(), e1(), e2(), e3(), e4());
  }

  public static class Strings extends SampleElements<String> {
    public Strings() {
      // elements aren't sorted, to better test SortedSet iteration ordering
      super("b", "a", "c", "d", "e");
    }

import com.google.common.collect.BenchmarkHelpers.SetImpl;
import com.google.common.collect.CollectionBenchmarkSampleData.Element;
import java.util.Set;
import org.jspecify.annotations.NullUnmarked;

/**
 * Test iteration speed at various size for {@link Set} instances.
 *
 * @author Christopher Swenson
 */
@NullUnmarked
public class SetIterationBenchmark {
  @Param({

import org.jspecify.annotations.Nullable;

/**
 * A {@code Multiset} implementation with predictable iteration order. Its iterator orders elements
 * according to when the first occurrence of the element was added. When the multiset contains
 * multiple instances of an element, those instances are consecutive in the iteration order. If all
 * occurrences of an element are removed, after which that element is added to the multiset, the

import org.jspecify.annotations.Nullable;

/**
 * A {@code Multiset} implementation with predictable iteration order. Its iterator orders elements
 * according to when the first occurrence of the element was added. When the multiset contains
 * multiple instances of an element, those instances are consecutive in the iteration order. If all
 * occurrences of an element are removed, after which that element is added to the multiset, the

import com.google.caliper.Param;
import com.google.common.base.Preconditions;
import java.util.Random;
import org.jspecify.annotations.NullUnmarked;

/**
 * Tests the speed of iteration of different iteration methods for collections.
 *
 * @author David Richter
 */
@NullUnmarked
public class MultisetIteratorBenchmark {
  @Param({"0", "1", "16", "256", "4096", "65536"})
  int size;