import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.concurrent.CopyOnWriteArraySet;
import java.util.function.BiConsumer;
import java.util.stream.Collector;
import java.util.stream.Stream;
import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Unit test for {@code Sets}.

import java.util.Map;
import java.util.NavigableMap;
import java.util.SortedMap;
import java.util.TreeMap;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**

import java.util.TreeMap;
import java.util.function.BiConsumer;
import java.util.function.BinaryOperator;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**

    @GwtIncompatible // java.io.ObjectOutputStream
    @J2ktIncompatible
    private void writeObject(ObjectOutputStream stream) throws IOException {
      synchronized (mutex) {
        stream.defaultWriteObject();
      }
    }

    @GwtIncompatible // not needed in emulated source
    @J2ktIncompatible
    private static final long serialVersionUID = 0;
  }

    result = Maps.fromProperties(testProp);
    assertEquals("true", result.get("first"));
    assertEquals("null", result.get("second"));
    assertEquals(2, result.size());

    // Now test values loaded from a stream.
    String props = "test\n second = 2\n Third item :   a short  phrase   ";

    testProp.load(new StringReader(props));

    result = Maps.fromProperties(testProp);
    assertEquals(4, result.size());

    result = Maps.fromProperties(testProp);
    assertEquals("true", result.get("first"));
    assertEquals("null", result.get("second"));
    assertEquals(2, result.size());

    // Now test values loaded from a stream.
    String props = "test\n second = 2\n Third item :   a short  phrase   ";

    testProp.load(new StringReader(props));

    result = Maps.fromProperties(testProp);
    assertEquals(4, result.size());

   * Iterables#filter(Iterable, Class)} for related functionality.)
   *
   * <p><b>Java 8+ users:</b> many use cases for this method are better addressed by {@link
   * java.util.stream.Stream#filter}. This method is not being deprecated, but we gently encourage
   * you to migrate to streams.
   */
  // TODO(kevinb): how to omit that last sentence when building GWT javadoc?

    private void writeObject(ObjectOutputStream stream) throws IOException {
      stream.defaultWriteObject();
      stream.writeObject(factory);
      stream.writeObject(backingMap());
    }

    @GwtIncompatible // java.io.ObjectInputStream
    @J2ktIncompatible
    @SuppressWarnings("unchecked") // reading data stored by writeObject
    private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {