public StringObjectId( String id ) {
    this.id = id;
  }
@Test
  public void testStringObjectId() {
    String expectedId = UUID.randomUUID().toString();
    StringObjectId obj = new StringObjectId( expectedId );
    assertEquals( expectedId, obj.getId() );
    assertEquals( expectedId, obj.toString() );
    assertEquals( expectedId.hashCode(), obj.hashCode() );
    assertFalse( obj.equals( null ) );
    assertTrue( obj.equals( obj ) );
    assertEquals( 0, obj.compareTo( obj ) );

    StringObjectId clone = new StringObjectId( obj );
    assertNotSame( obj, clone );
    assertEquals( obj.getId(), clone.getId() );
  }