jvm当Java线程运行时会发生什么。睡眠（100）？关于将netty的Write flush（）记录到ChannelHandlerContext的问题

Question

环境：

OS:win10
JDK:1.8
server: jetty-maven-plugin:9.2.1.v20140609 
netty:4.1.18.Final

问题:

在多线程环境中使用ChannelHandlerContext时。我必须睡眠100毫秒或更长时间才能成功发送数据，请查看代码段：

class A{
   public boolean sendData(int deviceId, String hexData){
     try {
         if (deviceChannel.containsKey(Integer.valueOf(deviceId))) {
         ChannelHandlerContext ctx = (ChannelHandlerContext)deviceChannel.get(Integer.valueOf(deviceId)); 
         byte[] data = Command.Trans(deviceId, hexData); 
    
         ByteBuf bufAck = ctx.alloc().buffer();
         bufAck.writeBytes(data);
         ctx.write(bufAck);
         ctx.flush();
         return true;
        }
     } catch (Exception e) {e.printStackTrace();}
      return false;
   }
}

**Class B:** I did not sleep in class B, the data did not send successfully
class B{
  
 public void  trans(){
       int iotAddr=123456;
       String hexData="01020000162C";
       A a=new A();
      boolean isTransSuccess=a.sendData(iotAddr, hexData); //return true,The client does not receive the data,Look at the class C.
 }
}


**Class C:**  I sleep for 100 milliseconds before calling the sendData() method and the data is sent successfully
class C{
    public void  trans(){
       int iotAddr=123456;
       String hexData="01020000162C";
       A a= new A();
       try {
        Thread.sleep(100);              // sleep for 100 ms or more
       } catch (InterruptedException e) {
           e.printStackTrace();
       }     
      boolean isTransSuccess=a.sendData(iotAddr, hexData);  //The client receives the data
   }
}

当JVM执行线程时会发生什么情况。睡眠（100）