Java Demo, Reading and Writing with Files

Notes:

• Example of reading from and writing to a text file.
• The process of opening files needs to be put inside a "try - catch" block
  in case there is a problem opening the file(s). In this example, the
  try-catch block catches an "IOException". "e" is the variable name for the
  IOException that may occur.
• The general format for opening a file uses three classes:
  BufferedReader, FileReader (for reading from files), and FileWriter (writing to files)
  
• The format for opening a file for reading is:
  BufferedReader infile=new BufferedReader(new FileReader(filename));
  "infile" is the user supplied name for the "instance" of this class created with new
  
• Check out:
  http://java.sun.com/j2se/1.3/docs/api/index.html for more info on
  these classes such as BufferedReader.
• To read a line from the text file: use the readLine() method from the
  BufferedReader class. Use this syntax: instance-name.readLine()
  In this program we use: line = infile.readLine()
• infile.readLine() returns a String. "line" is a String.
• outfile.write(line) writes the string "line" to a file specified by
  FileWriter().
  An alternative syntax is:
  outfile.write(line,0,line.length()); to write
  a specific portion of a string.
• outfile.newLine() generates a new line.

import java.io.*;   // Import the Input and Output Stream Classes

public class JavaDemo{
   public static void main(String[] args){
      try{
         BufferedReader infile =
                new BufferedReader(new FileReader("sampleFile.txt"));	  
                                               // Open for reading
         System.out.println("File open for reading...");
         BufferedWriter outfile = 
                   new BufferedWriter(new FileWriter("writefile.txt"));	
                               // Open for writing
         System.out.println("File open for writing...");
         String line;  
         while((line = infile.readLine()) != null)
         {
            System.out.println(line);	// routes output to CRT
            outfile.write(line); //writes to a file
         //Or use the following syntax to write a portion of a String:
         //   outfile.write(line, 0, line.length());  // routes output to file

            outfile.newLine();
         }
         System.out.println("Done copying file...");
         infile.close();
         outfile.close();
         System.out.println("Files closed.");
      }
      catch(IOException e){
            System.err.println(e);
            return;
}}}