// File: FileIO3.java
//
// Author: Rahul Simha
// Created: Aug, 1998.
//
// Illustrates reading from and writing to
// the same file. A file read into memory, modified
// and written out again.

import java.io.*;

public class FileIO3 {

    public static void main (String[] argv)
    {
	String filename = "testdata3";
	int numLines = 0;
	String[] lineBuffer = null;
	
	// First, we read in the file to get the size.
	try {
	    FileReader fr = new FileReader (filename);
	    LineNumberReader lr = new LineNumberReader (fr);
	    
	    boolean over = false;         
	    numLines = 0;
	    do {
		String input_line = lr.readLine ();
		if (input_line != null)
		    numLines ++;
		else
		    over = true;
	    } while (! over);
	    
	    lr.close();
	}
	catch (IOException e) {
	    System.out.println (e);
	}

	// We have now counted the number of lines and
	// we will read the file into a buffer.
	try {
	    FileReader fr = new FileReader (filename);
	    LineNumberReader lr = new LineNumberReader (fr);
	    
	    // Allocate necessary space.
	    lineBuffer = new String[numLines];
	    
	    int i = -1;
	    boolean over = false;
	    do {
		String s = lr.readLine ();
		if (s == null) 
		    over = true;
		else 
		    lineBuffer [++i] = s;
	    } while (! over);
	    
	    lr.close();
	}
	catch (IOException e) {
	    System.out.println (e);
	}
	
	// Next, write the buffer out to the same file
	// with line numbers added.
	try {
	    // Open the file for writing
	    FileWriter fr = new FileWriter (filename);
	    PrintWriter pw = new PrintWriter (fr);
	    
	    // Write from buffer with line numbers:
	    for (int i=0; i<numLines; i++) 
		pw.println ("Line " + (i+1) + ": " + lineBuffer[i]);
	    
	    pw.close();
	}
	catch (IOException e) {
	    System.out.println (e);
	}
	
    }

}