### Question:
DocumentKey implements Comparable<DocumentKey> { public DocumentKey() { } DocumentKey();  DocumentKey(long key);  DocumentKey(int hash, int revision, int version); long getKey(); int getHash(); int getRevision(); int getVersion(); @Override int hashCode(); @Override boolean equals(Object obj); static long toKey(int hash, int revision, int version); static long toDocumentId(long key); static int toHash(long key); static int toRevision(long key); static int toVersion(long key); @Override String toString(); @Override int compareTo(DocumentKey otherKey);  }### Answer:
@Test public void testDocumentKey() { DocumentKey key = new DocumentKey(1, 0, 0); System.out.println(key); assertEquals(key.getHash(), 1L); assertEquals(key.getRevision(), 0); assertEquals(key.getVersion(), 0); }