We all are familiar with reading/writing file in a synchronous way. In Java 7 a new API was added to read/write the contents of the file asynchronously. The API is AsynchronousFileChannel.
also read:
In this example lets look at how to read the contents of the file asynchronously. There are two approaches to read the contents asynchronously:
1. To use Future class to wait for the result of the read operation.
2. To use a callback defined by the CompletionHandler to process the result of the Asynchronous operation.
//Using Future class to read the contents of the file.
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousFileChannel;
import java.nio.charset.Charset;
import java.nio.file.*;
import java.util.concurrent.*;
public class AsyncFutureRead {
public static void main(String[] args) {
//Buffer to read the contents from the file.
ByteBuffer buffer = ByteBuffer.allocate(100);
//The file to read the contents from.
Path path = Paths.get('D:/tests/test.txt');
//Creating the asynchronous channel to the file which allows reading and writing of content.
try(AsynchronousFileChannel asyncChannel = AsynchronousFileChannel.open(path)){
//Returns a Future instance which can be used to read the contents of the file.
Future<Integer> fileResult = asyncChannel.read(buffer, 0);
//Waiting for the file reading to complete.
while(!fileResult.isDone()){
System.out.println('Waiting to complete the file reading ...');
}
//Print the number of bytes read.
System.out.println('Number of bytes read: '+fileResult.get());
//Reset the current position of the buffer to the beginning and the limit to the current position.
buffer.flip();
//Decode the contents of the byte buffer.
System.out.println('Contents of file: ');
System.out.println(Charset.defaultCharset().decode(buffer));
}catch(IOException | InterruptedException | ExecutionException ex){
ex.printStackTrace();
}
}
}
Pro Java 7 NIO.2 addresses the three primary elements that offer new input/output (I/O) APIs in Java 7, giving you the skills to write robust, scalable Java applications.
