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File Reading & Writing in Java

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In java, there multiple ways to read data from a file and to write data to a file. The most commonly used ways are as follows.

Using Byte Stream (FileInputStream and FileOutputStream)

Using Character Stream (FileReader and FileWriter)

Let's look each of these ways.

File Handling using Byte Stream

In java, we can use a byte stream to handle files. The byte stream has the following built-in classes to perform various operations on a file.

FileInputStream - It is a built-in class in java that allows reading data from a file. This class has implemented based on the byte stream. The FileInputStream class provides a method read() to read data from a file byte by byte.
FileOutputStream - It is a built-in class in java that allows writing data to a file. This class has implemented based on the byte stream. The FileOutputStream class provides a method write() to write data to a file byte by byte.

Let's look at the following example program that reads data from a file and writes the same to another file using FileInoutStream and FileOutputStream classes.

Example

import java.io.*;
public class FileReadingTest {

   public static void main(String args[]) throws IOException {  
      FileInputStream in = null;
      FileOutputStream out = null;

      try {
         in = new FileInputStream("C:\\Raja\\Input-File.txt");
         out = new FileOutputStream("C:\\Raja\\Output-File.txt");
         
         int c;
         while ((c = in.read()) != -1) {
            out.write(c);
         }
         System.out.println("Reading and Writing has been success!!!");
      }
      catch(Exception e){
    	  System.out.println(e);
      }finally {
         if (in != null) {
            in.close();
         }
         if (out != null) {
            out.close();
         }
      }
   }
}

When we run the above program, it produce the following output.

File Handling using Character Stream

In java, we can use a character stream to handle files. The character stream has the following built-in classes to perform various operations on a file.

FileReader - It is a built-in class in java that allows reading data from a file. This class has implemented based on the character stream. The FileReader class provides a method read() to read data from a file character by character.
FileWriter - It is a built-in class in java that allows writing data to a file. This class has implemented based on the character stream. The FileWriter class provides a method write() to write data to a file character by character.

Let's look at the following example program that reads data from a file and writes the same to another file using FIleReader and FileWriter classes.