return new Joiner(separator);
  }

  /** Returns a joiner which automatically places {@code separator} between consecutive elements. */
  public static Joiner on(char separator) {
    return new Joiner(String.valueOf(separator));
  }

  private final String separator;

  private Joiner(String separator) {
    this.separator = checkNotNull(separator);
  }

  private Joiner(Joiner prototype) {

  }

  private static void checkNoOutput(Joiner joiner, Iterable<Integer> set) {
    assertEquals("", joiner.join(set));
    assertEquals("", joiner.join(set.iterator()));

    Object[] array = Lists.newArrayList(set).toArray(new Integer[0]);
    assertEquals("", joiner.join(array));

    StringBuilder sb1FromIterable = new StringBuilder();
    assertSame(sb1FromIterable, joiner.appendTo(sb1FromIterable, set));

 *
 * @author Ben Yu
 */
@ElementTypesAreNonnullByDefault
final class Types {

  /** Class#toString without the "class " and "interface " prefixes */
  private static final Joiner COMMA_JOINER = Joiner.on(", ").useForNull("null");

  /** Returns the array type of {@code componentType}. */
  static Type newArrayType(Type componentType) {
    if (componentType instanceof WildcardType) {

  }

  @Generates
  <T> com.google.common.base.Optional<T> generateGoogleOptional(T value) {
    return com.google.common.base.Optional.of(value);
  }

  @Generates
  Joiner generateJoiner() {
    return Joiner.on(generateString());
  }

  @Generates
  Splitter generateSplitter() {
    return Splitter.on(generateString());
  }

  @Generates
  <T> Equivalence<T> generateEquivalence() {

    assertEquals("FooBar{}", toTest);
  }

  @GwtIncompatible // Class names are obfuscated in GWT
  public void testToStringHelper_localInnerClass() {
    // Local inner classes have names ending like "Outer.$1Inner"
    class LocalInnerClass {}
    String toTest = MoreObjects.toStringHelper(new LocalInnerClass()).toString();
    assertEquals("LocalInnerClass{}", toTest);
  }

   * cases where {@link Collection#contains} might throw {@link NullPointerException} or {@link
   * ClassCastException}.
   */
  // <? extends @Nullable Object> instead of <?> because of Kotlin b/189937072, discussed in Joiner.
  public static boolean contains(
      Iterable<? extends @Nullable Object> iterable, @CheckForNull Object element) {
    if (iterable instanceof Collection) {
      Collection<?> collection = (Collection<?>) iterable;

import static org.junit.Assert.assertThrows;

import com.google.common.collect.ImmutableSet;
import java.util.HashSet;
import java.util.Set;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

@RunWith(JUnit4.class)
public final class InvalidatableSetTest {
  Set<Integer> wrappedSet;
  Set<Integer> copyOfWrappedSet;
  InvalidatableSet<Integer> setToTest;

import static org.junit.Assert.assertThrows;

import com.google.common.collect.ImmutableSet;
import java.util.HashSet;
import java.util.Set;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

@RunWith(JUnit4.class)
public final class InvalidatableSetTest {
  Set<Integer> wrappedSet;
  Set<Integer> copyOfWrappedSet;
  InvalidatableSet<Integer> setToTest;

 * please see {@link com.google.common.collect.testing.CollectionTestSuiteBuilder}.
 *
 * @author Jared Levy
 */
@GwtCompatible
@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
public class QueuePollTester<E> extends AbstractQueueTester<E> {
  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(ZERO)
  public void testPoll_empty() {

 * directly; please see {@link com.google.common.collect.testing.ListTestSuiteBuilder}.
 *
 * @author Chris Povirk
 */
@GwtCompatible
@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
public class ListRetainAllTester<E> extends AbstractListTester<E> {
  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = {ZERO, ONE})