code: import java.io.FileOutputStream;
  import java.io.IOException;
  import java.nio.channels.FileChannel;
  
  public class TruncFile {
  	public static void main(String[] args) throws IOException{
  		if(args.length < 2){
  			System.out.println("Usage: java TruncFile fileName newSize");
  			return;
  		}
  		//turn on "append" so it doesn't clear the file
  		FileChannel outChan = new FileOutputStream(args[0], true).getChannel();
  		long newSize = Long.parseLong(args[1]);
  		outChan.truncate(newSize);
  		outChan.close();
  	}
  }
  