Java Reference
In-Depth Information
Listing 10-24.
Using a Future Object to Handle the Result of an Asynchronous File Read
// AsyncFileReadFuture.java
package com.jdojo.nio2;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.nio.ByteBuffer;
import java.io.IOException;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.channels.AsynchronousFileChannel;
import java.nio.charset.Charset;
import static java.nio.file.StandardOpenOption.READ;
public class AsyncFileReadFuture {
public static void main(String[] args) {
Path path = Paths.get("rainbow.txt");
try (AsynchronousFileChannel afc =
AsynchronousFileChannel.open(path, READ)) {
// Get a data buffer of the file size to read
int fileSize = (int)afc.size();
ByteBuffer dataBuffer = ByteBuffer.allocate(fileSize);
// Perform the asynchronous read operation
Future<Integer> result = afc.read(dataBuffer, 0);
System.out.println("Waiting for reading to be finished...");
try {
// Let us wait until reading is finished
int readBytes = result.get();
System.out.format("%s bytes read from %s%n", readBytes, path);
System.out.format("Read data is:%n");
// Read the data from the buffer
byte[] byteData = dataBuffer.array();
Charset cs = Charset.forName("UTF-8");
String data = new String(byteData, cs);
System.out.println(data);
}
catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
}
catch (IOException ex) {
ex.printStackTrace();
}
}
}
