Reading from a file using the AsynchronousFileChannel class : Asynchronous Channel « JDK 7 « Java

1. Java
2. JDK 7
3. Asynchronous Channel

Reading from a file using the AsynchronousFileChannel class

import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousFileChannel;
import java.nio.channels.CompletionHandler;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.EnumSet;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class Test {

  public static void main(String args[]) throws Exception {
    ExecutorService pool = new ScheduledThreadPoolExecutor(3);
    AsynchronousFileChannel fileChannel = AsynchronousFileChannel.open(
        Paths.get("data.txt"), EnumSet.of(StandardOpenOption.READ),
        pool);
    CompletionHandler<Integer, ByteBuffer> handler = new CompletionHandler<Integer, ByteBuffer>() {
      @Override
      public synchronized void completed(Integer result, ByteBuffer attachment) {
        for (int i = 0; i < attachment.limit(); i++) {
          System.out.println((char) attachment.get(i));
        }
      }
      @Override
      public void failed(Throwable e, ByteBuffer attachment) {
      }
    };
    final int bufferCount = 5;
    ByteBuffer buffers[] = new ByteBuffer[bufferCount];
    for (int i = 0; i < bufferCount; i++) {
      buffers[i] = ByteBuffer.allocate(10);
      fileChannel.read(buffers[i], i * 10, buffers[i], handler);
    }
    pool.awaitTermination(1, TimeUnit.SECONDS);
    for (ByteBuffer byteBuffer : buffers) {
      for (int i = 0; i < byteBuffer.limit(); i++) {
        System.out.print((char) byteBuffer.get(i));
      }
    }
  }
}

 

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