var directByteBuffer = ByteBuffer.allocateDirect(1024);
assert directByteBuffer.isDirect(); 

var heapByteBuffer = ByteBuffer.allocate(1024);
assert !heapByteBuffer.isDirect(); 
 
var byteBufferByWrap = ByteBuffer.wrap("hello".getBytes()); 
assert !byteBufferByWrap.isDirect();

// ...
 
@Slf4j
public class Example1_FileChannelRead {
  @SneakyThrows
  public static void main(String [] args){
    log.info("main function started");
 
    var path = Example1_FileChannelRead.class
        .getClassLoader()
        .getResource("example1-data.txt")
        .getFile();
 
    var file = new File(path);
 
    try (var fileChannel = FileChannel.open(file.toPath())){
      var byteBuffer = ByteBuffer.allocateDirect(1024);
      bufferLog("버퍼할당", byteBuffer);
 
 
      fileChannel.read(byteBuffer);
      bufferLog("읽기 연산(read) - 버퍼에 쓰는 작업", byteBuffer);
 
      byteBuffer.flip();
      bufferLog("읽기 전환(Flip)", byteBuffer);
 
      byteBuffer.rewind();
      bufferLog("첫 위치로 전환(rewind)", byteBuffer);
 
      log.info("buffer = {}", StandardCharsets.UTF_8.decode(byteBuffer));
      bufferLog("Buffer연산 없이 decode 수행", byteBuffer);
 
      log.info("buffer = {}", StandardCharsets.UTF_8.decode(byteBuffer));
      bufferLog("Buffer연산 없이 decode 수행", byteBuffer);
 
      byteBuffer.clear();
      bufferLog("clear", byteBuffer);
    }
 
    log.info("main function end");
  }
 
  public static void bufferLog(String operation, ByteBuffer buffer){
    log.info(String.format("%s >>> position = %s, limit = %s, capacity = %s\n", operation, buffer.position(), buffer.limit(), buffer.capacity()));
  }
}
 

NVIDIA Corporation provides graphics, and compute and networking solutions in the United States, Taiwan, China, Hong Kong, and internationally. The Graphics segment offers GeForce GPUs for gaming and PCs, the GeForce NOW game streaming service and related infrastructure, and solutions for gaming platforms; Quadro/NVIDIA RTX GPUs for enterprise workstation graphics; virtual GPU or vGPU software for cloud-based visual and virtual computing; automotive platforms for infotainment systems; and Omniverse software for building and operating metaverse and 3D internet applications. The Compute & Networking segment comprises Data Center computing platforms and end-to-end networking platforms, including Quantum for InfiniBand and Spectrum for Ethernet; NVIDIA DRIVE automated-driving platform and automotive development agreements; Jetson robotics and other embedded platforms; NVIDIA AI Enterprise and other software; and DGX Cloud software and services. The company's products are used in gaming, professional visualization, data center, and automotive markets. It sells its products to original equipment manufacturers, original device manufacturers, system integrators and distributors, independent software vendors, cloud service providers, consumer internet companies, add-in board manufacturers, distributors, automotive manufacturers and tier-1 automotive suppliers, and other ecosystem participants. NVIDIA Corporation was incorporated in 1993 and is headquartered in Santa Clara, California.
출처 : https://finance.yahoo.com/quote/NVDA/profile

08:44:52.388 [main] INFO io...Example1_FileChannelRead -- main function started
08:44:52.407 [main] INFO io...Example1_FileChannelRead -- 버퍼할당 >>> position = 0, limit = 1024, capacity = 1024

08:44:52.407 [main] INFO io...Example1_FileChannelRead -- 읽기 연산(read) - 버퍼에 쓰는 작업 >>> position = 1024, limit = 1024, capacity = 1024

08:44:52.408 [main] INFO io...Example1_FileChannelRead -- 읽기 전환(Flip) >>> position = 0, limit = 1024, capacity = 1024

08:44:52.408 [main] INFO io...Example1_FileChannelRead -- 첫 위치로 전환(rewind) >>> position = 0, limit = 1024, capacity = 1024

08:44:52.409 [main] INFO io...Example1_FileChannelRead -- buffer = NVIDIA Corporation provides graphics, and compute and networking solutions in the United States, Taiwan, China, Hong Kong, and internationally. The Graphics segment offers GeForce GPUs for gaming and PCs, the GeForce NOW game streaming service and related infrastructure, and solutions for gaming platforms; Quadro/NVIDIA RTX GPUs for enterprise workstation graphics; virtual GPU or vGPU software for cloud-based visual and virtual computing; automotive platforms for infotainment systems; and Omniverse software for building and operating metaverse and 3D internet applications. The Compute & Networking segment comprises Data Center computing platforms and end-to-end networking platforms, including Quantum for InfiniBand and Spectrum for Ethernet; NVIDIA DRIVE automated-driving platform and automotive development agreements; Jetson robotics and other embedded platforms; NVIDIA AI Enterprise and other software; and DGX Cloud software and services. The company's products are used in gaming, professional visualization
08:44:52.412 [main] INFO io...Example1_FileChannelRead -- Buffer연산 없이 decode 수행 >>> position = 1024, limit = 1024, capacity = 1024

08:44:52.412 [main] INFO io...Example1_FileChannelRead -- buffer = 
08:44:52.412 [main] INFO io...Example1_FileChannelRead -- Buffer연산 없이 decode 수행 >>> position = 1024, limit = 1024, capacity = 1024

08:44:52.412 [main] INFO io...Example1_FileChannelRead -- clear >>> position = 0, limit = 1024, capacity = 1024

08:44:52.412 [main] INFO io...Example1_FileChannelRead -- main function end

Process finished with exit code 0

try (var serverChannel = ServerSocketChannel.open()){
    var address = new InetSocketAddress("localhost", 8080);
    serverChannel.bind(address);
    serverChannel.configureBlocking(false); /// nonblocking 설정 
    
    var clientSocket = serverChannel.accept(); 
    assert clientSocket !== null;
}

try (var socketChannel = SocketChannel.open()){
    var address = new InetSocketAddress("localhost", 8080);
    socketChannel.configureBlocking(false);
    var connected = socketChannel.connect(address);
    assert !connected;
}