### Question:
OID implements ID { public static OID get(final Object obj) { if (obj == null) { return NULL; } return new OID(obj.getClass().getName(), System.identityHashCode(obj)); } private  OID(final String type, final int hash); private  OID(); String getType(); int getHash(); @Override boolean equals(final Object obj); @Override int hashCode(); @Override String toString(); static OID get(final Object obj); static OID oid(final Object obj); static OID parse(final String spec); static String render(final Object obj); static T find(final Collection<T> items, final String id); static T find(final Collection<T> items, final OID id); static final OID NULL; }### Answer:
@Test public void testGetNull() { OID oid = OID.get(null); assertEquals(OID.NULL, oid); }