public void testSerial() {
    assertTrue(_nbhm.isEmpty());
    final String k1 = "k1";
    final String k2 = "k2";
    assertThat(_nbhm.put(k1, "v1"), nullValue());
    assertThat(_nbhm.put(k2, "v2"), nullValue());

    // Serialize it out
    try {
      FileOutputStream fos = new FileOutputStream("NBHM_test.txt");
      ObjectOutputStream out = new ObjectOutputStream(fos);
      out.writeObject(_nbhm);
      out.close();
    } catch (IOException ex) {
      ex.printStackTrace();
    }

    // Read it back
    try {
      File f = new File("NBHM_test.txt");
      FileInputStream fis = new FileInputStream(f);
      ObjectInputStream in = new ObjectInputStream(fis);
      NonBlockingIdentityHashMap nbhm = (NonBlockingIdentityHashMap) in.readObject();
      in.close();
      assertThat(
          "serialization works",
          nbhm.toString(),
          anyOf(is("{k1=v1, k2=v2}"), is("{k2=v2, k1=v1}")));
      if (!f.delete()) throw new IOException("delete failed");
    } catch (IOException ex) {
      ex.printStackTrace();
    } catch (ClassNotFoundException ex) {
      ex.printStackTrace();
    }
  }
  /** A deserialized map equals original */
  public void testSerialization() throws Exception {
    ConcurrentNavigableMap q = map5();

    ByteArrayOutputStream bout = new ByteArrayOutputStream(10000);
    ObjectOutputStream out = new ObjectOutputStream(new BufferedOutputStream(bout));
    out.writeObject(q);
    out.close();

    ByteArrayInputStream bin = new ByteArrayInputStream(bout.toByteArray());
    ObjectInputStream in = new ObjectInputStream(new BufferedInputStream(bin));
    ConcurrentNavigableMap r = (ConcurrentNavigableMap) in.readObject();
    assertEquals(q.size(), r.size());
    assertTrue(q.equals(r));
    assertTrue(r.equals(q));
  }