File IO Operation in Java

Summary

The following is a simple example on how to read & write data from a file. For Writing data we need following objects

File Object -> FileWriter Object -> PrintWriter Object

For Reading data we need following objects

File Object -> FileReader Object -> BufferedReader Object

Screenshot

Code

package com.rohansakhale.ioprogram;

import java.io.*;

/**
 *
 * @author Rohan Sakhale
 */
public class WriteReadDemo {

    public static void main(String[] args) throws Exception{
        // Lets create an object for writing data onto a file
        // For that we will need object in following manner
        // File -> FileWriter -> BufferedWriter -> PrintWriter
        // PrintWriter will do all the job of writing data onto file
        
        String filePath = "1rohan_test.txt";
        // The best way to get the default directory of system
        // for windows it chooses desktop for writing this file
        
        File file = new File(filePath);
        FileWriter fw = new FileWriter(file); 
        // fw tends to throw IOException
        
        BufferedWriter bw = new BufferedWriter(fw);
        
        PrintWriter pw = new PrintWriter(bw, true);
        
        // true states to flush automatically
        // if not set true you can use following line whenever you need to flush
        // pw.flush();
        
        pw.println("Rohan testing file writing");
        pw.println("Using PrintWriter Class");
        
        // The above lines should write data to file.
        // For Vista & Seven users, make sure to select the path with file writable permissions
        // Over here I used, My Documents path for file writing
        
        // Lets read the written content from file onto console now
        // For that you will need the following objects
        // File -> FileReader -> BufferedReader
        // we will use the same file object as above
        
        FileReader fr = new FileReader(file);
        // fr tends to throw IOException
        
        BufferedReader br = new BufferedReader(fr);
        
        String str = br.readLine(); // Reads the entire one line of text at once
        while(str != null) // Checks if the string being read is not null
        {
            System.out.println(str);
            str = br.readLine();
            // Runs untill it does not reach end of file.
        }
        
        // Closing the opened string
        bw.close();
        br.close();
        pw.close();
        
    }
}