Writing Varying Length Strings 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.channels.FileChannel;
public class MainClass {
  public static void main(String[] args) {
    String dirName = "c:/test";
    String fileName = "test.txt";
    String[] sayings = { "A1", "B12", "C123", "D1234", "E12345", "F123456", "G1234567" };
    File aFile = new File(dirName, fileName);
    FileOutputStream outputFile = null;
    try {
      outputFile = new FileOutputStream(aFile, true);
    } catch (FileNotFoundException e) {
      e.printStackTrace(System.err);
      System.exit(1);
    }
    FileChannel outChannel = outputFile.getChannel();
    int maxLength = 0;
    for (String saying : sayings) {
      if (maxLength < saying.length()){
        maxLength = saying.length();
      }
    }
    ByteBuffer buf = ByteBuffer.allocate(2 * maxLength + 4);
    try {
      for (String saying : sayings) {
        buf.putInt(saying.length()).asCharBuffer().put(saying);
        buf.position(buf.position() + 2 * saying.length()).flip();
        outChannel.write(buf);
        buf.clear();
      }
      outputFile.close();
    } catch (IOException e) {
      e.printStackTrace(System.err);
    }
  }
}