Enumeration<T> enumeration) {
    checkNotNull(enumeration);
    return new UnmodifiableIterator<T>() {
      @Override
      public boolean hasNext() {
        return enumeration.hasMoreElements();
      }

      @Override
      @ParametricNullness
      public T next() {
        return enumeration.nextElement();
      }
    };
  }

      Enumeration<T> enumeration) {
    checkNotNull(enumeration);
    return new UnmodifiableIterator<T>() {
      @Override
      public boolean hasNext() {
        return enumeration.hasMoreElements();
      }

      @Override
      @ParametricNullness
      public T next() {
        return enumeration.nextElement();
      }
    };
  }

    Enumeration<Integer> enumer = Iterators.asEnumeration(iter);

    assertFalse(enumer.hasMoreElements());
    assertThrows(NoSuchElementException.class, () -> enumer.nextElement());
  }

  public void testAsEnumerationSingleton() {
    Iterator<Integer> iter = ImmutableList.of(1).iterator();
    Enumeration<Integer> enumer = Iterators.asEnumeration(iter);

    Enumeration<Integer> enumer = Iterators.asEnumeration(iter);

    assertFalse(enumer.hasMoreElements());
    assertThrows(NoSuchElementException.class, () -> enumer.nextElement());
  }

  public void testAsEnumerationSingleton() {
    Iterator<Integer> iter = ImmutableList.of(1).iterator();
    Enumeration<Integer> enumer = Iterators.asEnumeration(iter);

  @GwtIncompatible // Maps.fromProperties
  public void testFromPropertiesNullKey() {
    Properties properties =
        new Properties() {
          @Override
          public Enumeration<?> propertyNames() {
            return Iterators.asEnumeration(asList(null, "first", "second").iterator());
          }
        };
    properties.setProperty("first", "true");
    properties.setProperty("second", "null");

import java.net.Proxy;
import java.net.Proxy.Type;
import java.net.SocketAddress;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Date;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;