### Question:
ByteBufList extends AbstractReferenceCounted { @Override public ByteBufList retain() { super.retain(); return this; } private  ByteBufList(Handle<ByteBufList> recyclerHandle); static ByteBufList get(ByteBuf b1, ByteBuf b2); static ByteBufList get(ByteBuf b1); static ByteBufList clone(ByteBufList other); void add(ByteBuf buf); void prepend(ByteBuf buf); int readableBytes(); ByteBuf getBuffer(int index); int size(); int getBytes(byte[] dst); byte[] toArray(); boolean hasArray(); byte[] array(); int arrayOffset(); @VisibleForTesting static ByteBuf coalesce(ByteBufList list); @Override ByteBufList retain(); @Override ReferenceCounted touch(Object hint); static final Encoder ENCODER; static final Encoder ENCODER_WITH_SIZE; }### Answer:
@Test public void testRetain() throws Exception { ByteBuf b1 = PooledByteBufAllocator.DEFAULT.heapBuffer(128, 128); b1.writerIndex(b1.capacity()); ByteBufList buf = ByteBufList.get(b1); assertEquals(1, buf.size()); assertEquals(128, buf.readableBytes()); assertEquals(b1, buf.getBuffer(0)); assertEquals(buf.refCnt(), 1); assertEquals(b1.refCnt(), 1); buf.retain(); assertEquals(buf.refCnt(), 2); assertEquals(b1.refCnt(), 1); buf.release(); assertEquals(buf.refCnt(), 1); assertEquals(b1.refCnt(), 1); buf.release(); assertEquals(buf.refCnt(), 0); assertEquals(b1.refCnt(), 0); }