### Question:
FixedChannelPool extends SimpleChannelPool { @Override public Future<Channel> acquire(final Promise<Channel> promise) { try { if (executor.inEventLoop()) { acquire0(promise); } else { executor.execute(new Runnable() { @Override public void run() { acquire0(promise); } }); } } catch (Throwable cause) { promise.setFailure(cause); } return promise; } FixedChannelPool(Bootstrap bootstrap,
                            ChannelPoolHandler handler, int maxConnections);  FixedChannelPool(Bootstrap bootstrap,
                            ChannelPoolHandler handler, int maxConnections, int maxPendingAcquires);  FixedChannelPool(Bootstrap bootstrap,
                            ChannelPoolHandler handler,
                            ChannelHealthChecker healthCheck, AcquireTimeoutAction action,
                            final long acquireTimeoutMillis,
                            int maxConnections, int maxPendingAcquires);  FixedChannelPool(Bootstrap bootstrap,
                            ChannelPoolHandler handler,
                            ChannelHealthChecker healthCheck, AcquireTimeoutAction action,
                            final long acquireTimeoutMillis,
                            int maxConnections, int maxPendingAcquires, final boolean releaseHealthCheck);  FixedChannelPool(Bootstrap bootstrap,
                            ChannelPoolHandler handler,
                            ChannelHealthChecker healthCheck, AcquireTimeoutAction action,
                            final long acquireTimeoutMillis,
                            int maxConnections, int maxPendingAcquires,
                            boolean releaseHealthCheck, boolean lastRecentUsed); int acquiredChannelCount(); @Override Future<Channel> acquire(final Promise<Channel> promise); @Override Future<Void> release(final Channel channel, final Promise<Void> promise); @Override void close();  }### Answer:
@Test public void testAcquire() throws Exception { LocalAddress addr = new LocalAddress(LOCAL_ADDR_ID); Bootstrap cb = new Bootstrap(); cb.remoteAddress(addr); cb.group(group) .channel(LocalChannel.class); ServerBootstrap sb = new ServerBootstrap(); sb.group(group) .channel(LocalServerChannel.class) .childHandler(new ChannelInitializer<LocalChannel>() { @Override public void initChannel(LocalChannel ch) throws Exception { ch.pipeline().addLast(new ChannelInboundHandlerAdapter()); } }); Channel sc = sb.bind(addr).syncUninterruptibly().channel(); CountingChannelPoolHandler handler = new CountingChannelPoolHandler(); ChannelPool pool = new FixedChannelPool(cb, handler, 1, Integer.MAX_VALUE); Channel channel = pool.acquire().syncUninterruptibly().getNow(); Future<Channel> future = pool.acquire(); assertFalse(future.isDone()); pool.release(channel).syncUninterruptibly(); assertTrue(future.await(1, TimeUnit.SECONDS)); Channel channel2 = future.getNow(); assertSame(channel, channel2); assertEquals(1, handler.channelCount()); assertEquals(1, handler.acquiredCount()); assertEquals(1, handler.releasedCount()); sc.close().syncUninterruptibly(); channel2.close().syncUninterruptibly(); }