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

1. Java Tutorial
2. File
3. FileChannel

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.DoubleBuffer;
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.txt");
    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);
    DoubleBuffer doubleBuf = buf.asDoubleBuffer();
    buf.position(8);
    CharBuffer charBuf = buf.asCharBuffer();
    for (long prime : primes) {
      String primeStr = "prime = " + prime;
      doubleBuf.put(0, (double) primeStr.length());
      charBuf.put(primeStr);
      buf.position(2 * charBuf.position() + 8);
      LongBuffer longBuf = buf.asLongBuffer();
      longBuf.put(prime);
      buf.position(buf.position() + 8);
      buf.flip();
      try {
        file.write(buf);
      } catch (IOException e) {
        e.printStackTrace(System.err);
      }
      buf.clear();
      doubleBuf.clear();
      charBuf.clear();
    }
    try {
      System.out.println("File written is " + file.size() + "bytes.");
      outputFile.close();
    } catch (IOException e) {
      e.printStackTrace(System.err);
    }
  }
}