String result = StringUtil.join(null, "first", "second", "third");
        assertEquals("firstnullsecondnullthird", result);
    }

    @Test
    @DisplayName("Should handle null elements in array")
    void testJoinWithNullElements() {
        String result = StringUtil.join(",", "first", null, "third");
        assertEquals("first,null,third", result);
    }

    @Test

        } else {
            fail("Inconsistent behavior: first=" + first + ", second=" + second);
        }

        // Third call should return the same cached Subject instance
        Subject third = auth.getSubject();
        assertEquals(second, third, "Subsequent calls should return same cached result");

        // Refresh should clear the cache
        auth.refresh();

        assertEquals("file2.txt", second.getName());

        assertTrue(iterator.hasNext(), "Should have third element");
        SmbResource third = iterator.next();
        assertNotNull(third, "Third element should not be null");
        assertEquals("file3.txt", third.getName());

        assertFalse(iterator.hasNext(), "Should not have more elements");
    }

    /**

        byte[] third = impl.getBuffer(); // cache empty -> new with size 3

        assertSame(a, first, "First get should return first cached buffer");
        assertSame(c, second, "Second get should return second cached buffer");
        assertNotSame(d, third, "Third get should allocate a new buffer (not the dropped one)");

        list.add(null);
        list.add("third");
        final byte[] binary = SerializeUtil.fromObjectToBinary(list);
        @SuppressWarnings("unchecked")
        final List<String> result = (List<String>) SerializeUtil.fromBinaryToObject(binary);
        assertEquals(3, result.size());
        assertEquals("first", result.get(0));
        assertNull(result.get(1));
        assertEquals("third", result.get(2));
    }

    /**

        CommonServerMessageBlockResponse second = response.getNextResponse();
        CommonServerMessageBlockResponse third = second.getNextResponse();
        CommonServerMessageBlockResponse end = third.getNextResponse();

        // Then
        assertEquals(nextResponse, second);
        assertEquals(thirdResponse, third);
        assertNull(end);
    }

    @Test

        CommonServerMessageBlockRequest third = second.getNext();
        CommonServerMessageBlockRequest fourth = third.getNext();
        boolean firstAllowsSecond = request.allowChain(nextRequest);
        boolean secondAllowsThird = nextRequest.allowChain(thirdRequest);

        // Then
        assertEquals(nextRequest, second);
        assertEquals(thirdRequest, third);
        assertNull(fourth);

        assertSame(fe2, it.next(), "Second element must match first page");

        // Next page fetched via fetchMore()
        assertTrue(it.hasNext(), "Iterator should have third element after fetchMore");
        assertSame(fe3, it.next(), "Third element from second page");

        // After last element, hasNext should be false and calling close() should send Smb2CloseRequest once

   * ClosingFuture)} to start this combination.
   *
   * @param <V1> the type returned by the first future
   * @param <V2> the type returned by the second future
   * @param <V3> the type returned by the third future
   */
  public static final class Combiner3<
          V1 extends @Nullable Object, V2 extends @Nullable Object, V3 extends @Nullable Object>
      extends Combiner {
    /**

            DfsReferralDataImpl third = new DfsReferralDataImpl();

            referralData.append(second);
            assertEquals(second, referralData.next());
            assertEquals(referralData, second.next());

            referralData.append(third);
            assertEquals(third, referralData.next());
            assertEquals(second, third.next());
            assertEquals(referralData, second.next());