Writing Numerical Data to a File : FileChannel « File « Java Tutorial

1. Java Tutorial
2. File
3. FileChannel

import static java.lang.Math.min;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.LongBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String[] args) {
    long[] primes = new long[] { 1, 2, 3, 5, 7 };
    File aFile = new File("C:/test/primes.bin");
    FileOutputStream outputFile = null;
    try {
      outputFile = new FileOutputStream(aFile);
    } catch (FileNotFoundException e) {
      e.printStackTrace(System.err);
    }
    FileChannel file = outputFile.getChannel();
    final int BUFFERSIZE = 100;
    ByteBuffer buf = ByteBuffer.allocate(BUFFERSIZE);
    LongBuffer longBuf = buf.asLongBuffer();
    int primesWritten = 0;
    while (primesWritten < primes.length) {
      longBuf.put(primes, primesWritten, min(longBuf.capacity(), primes.length - primesWritten));
      buf.limit(8 * longBuf.position());
      try {
        file.write(buf);
        primesWritten += longBuf.position();
      } catch (IOException e) {
        e.printStackTrace(System.err);
      }
      longBuf.clear();
      buf.clear();
    }
    try {
      System.out.println("File written is " + file.size() + "bytes.");
      outputFile.close();
    } catch (IOException e) {
      e.printStackTrace(System.err);
    }
  }
}