/* Written by Jen Chen
   Updated on March the 4th, 2003
   Copyrighted by Jen Chen
   Note: Random Access file can only be used if all fields in your file have fixed width.
   	 Even if there is one field without a fixed width, then we can not use random access 
   	 file to get to the desired field (or record).
   	 One way to deal with this situation is to pad all fields with white spaces so that
   	 each field has a fixed number of characters, then we should be able to go to a specific
   	 field since now we can based on the number of bytes to get to the field/record that we
   	 want to go to.
*/
import java.io.*;
import java.util.*;

public class RandomAccess4{
  public static void main(String[] args) throws InterruptedException, IOException {
     int maxsize = 100;
     String outfile = "num.csv";
     File out = new File(outfile);
     BufferedWriter outbuf = new BufferedWriter(new FileWriter(outfile));

     for (int i=0; i < maxsize; i++){   // random generator
          if((i + 1)%10 != 0)
            outbuf.write((int) (1000*Math.random()) + ",");
          else
            outbuf.write((int) (1000*Math.random()) + "\n");
     }
     outbuf.close(); //Remember to close the file. Otherwise it is still waiting for input.

    BufferedReader inbuf = new BufferedReader(new FileReader(outfile));
    String line = null;
    line = inbuf.readLine(); //read into the first line of the file num.csv

    RandomAccessFile raf = new RandomAccessFile(outfile, "r");
    myMax2 newMax = new myMax2(outfile);
    long pointerEnd = raf.length()/2;
//    newMax.run(raf, 0, pointerEnd);

    long pointerStart = pointerEnd;
    pointerEnd = raf.length();
    newMax.run(raf, 0, pointerEnd);
        System.out.println(newMax.getMax());
      int mymax = newMax.getMax();
    newMax.run(raf,pointerStart, pointerEnd);
        System.out.println(newMax.getMax());
      int mymax2 = newMax.getMax();
    System.out.println("The maximum integer from the file is: " + Math.max(mymax, mymax2));
  } //end of main()
}//end of class MaxTest{}

class myMax2 extends Thread {
  String obj = null;
  private RandomAccessFile raf;
  private String line;
  private int max;

    public myMax2(){ }
    public myMax2(String st) throws IOException{
      this.obj = st;
      raf = new RandomAccessFile(obj, "r");
      }
  public void run(RandomAccessFile raf, long pointerStart, long pointerEnd) throws IOException{
//  public void run(RandomAccessFile raf) throws IOException{
//    long pos = 0, pointerstart = 0;
    long pos = 0, pointerE = pointerEnd;
//    pointerstart = raf.length()/2;
    int tmp = 0;
    max = 0;
    StringTokenizer stToken = null;
    raf.seek(pointerStart); //Start from the beginning of the file.

    while(raf.getFilePointer() < pointerE){ // pointerstart + 4 = the end of the pointer + 4 bytes (since an integer contains 4 bytes. So that it will read all values up to the middle of the file)
      pos = raf.getFilePointer();
      line = raf.readLine();
      stToken = new StringTokenizer(line, ",");
      while(stToken.hasMoreTokens()){
//        System.out.println(stToken.nextToken());
      tmp = Integer.parseInt(stToken.nextToken());
//      System.out.println("tmp = " + tmp);
      if(max <= tmp){ max = tmp;}

      }//end of inner WHILE()
    }//end of outer WHILE()
//  System.out.println(max);
  }  //end of run()

  public int getMax(){return max;}
}//end of class FindMax{}