import java.util.stream.Collector;
import java.util.stream.Collectors;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link NavigableMap} whose contents will never change, with many other important properties
 * detailed at {@link ImmutableCollection}.
 *
 * <p><b>Warning:</b> as with any sorted collection, you are strongly advised not to use a {@link

    assertNotSame(System.getProperty("java.version"), result.get("java.version"));
  }

  @J2ktIncompatible
  @GwtIncompatible // Maps.fromProperties
  @SuppressWarnings("serial") // never serialized
  public void testFromPropertiesNullKey() {
    Properties properties =
        new Properties() {
          @Override
          public Enumeration<?> propertyNames() {

    assertNotSame(System.getProperty("java.version"), result.get("java.version"));
  }

  @J2ktIncompatible
  @GwtIncompatible // Maps.fromProperties
  @SuppressWarnings("serial") // never serialized
  public void testFromPropertiesNullKey() {
    Properties properties =
        new Properties() {
          @Override
          public Enumeration<?> propertyNames() {

      synchronized (mutex) {
        /*
         * toArrayImpl returns `@Nullable Object[]` rather than `Object[]` but only because it can
         * be used with collections that may contain null. This collection never contains nulls, so
         * we could return `Object[]`. But this class is private and J2KT cannot change return types
         * in overrides, so we declare `@Nullable Object[]` as the return type.
         */

      while (iterator.hasNext()) {
        if (element.equals(iterator.next())) {
          return true;
        }
      }
    }
    return false;
  }

  /**
   * Traverses an iterator and removes every element that belongs to the provided collection. The
   * iterator will be left exhausted: its {@code hasNext()} method will return {@code false}.
   *
   * @param removeFrom the iterator to (potentially) remove elements from

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   *       exceptions).
   * </ul>
   *
   * <p>The overall principle is to continue to treat every checked exception as a checked
   * exception, every unchecked exception as an unchecked exception, and every error as an error. In
   * addition, the cause of any {@code ExecutionException} is wrapped in order to ensure that the
   * new stack trace matches that of the current thread.

 * cache after the iterator is created, it is undefined which of these changes, if any, are
 * reflected in that iterator. These iterators never throw {@link ConcurrentModificationException}.
 *
 * <p><b>Note:</b> by default, the returned cache uses equality comparisons (the {@link
 * Object#equals equals} method) to determine equality for keys or values. However, if {@link

      while (iterator.hasNext()) {
        if (element.equals(iterator.next())) {
          return true;
        }
      }
    }
    return false;
  }

  /**
   * Traverses an iterator and removes every element that belongs to the provided collection. The
   * iterator will be left exhausted: its {@code hasNext()} method will return {@code false}.
   *
   * @param removeFrom the iterator to (potentially) remove elements from

   * underlying multimap.
   *
   * <p>The returned multimap isn't threadsafe or serializable, even if {@code unfiltered} is.
   *
   * <p>Many of the filtered multimap's methods, such as {@code size()}, iterate across every
   * key/value mapping in the underlying multimap and determine which satisfy the filter. When a
   * live view is <i>not</i> needed, it may be faster to copy the filtered multimap and use the
   * copy.
   *