Java program to Read a Text file and Write to another File

In this Java tutorial, we will learn- How to develop a Java program to Read a Text file and Write to another File. In Java programming, there are 10’s of classes and 100’s of methods to manage a single file, but don’t get confused, Let’s solve this File management problem by following some simple techniques –

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Required Prior Knowledge and Steps

To understand this Java program to read a text file and write to another file, you must have a basic understanding of a few of Core Java concepts, like :

• Manipulating String and using its methods as String split(),
• Fundamental Loops in Java and,
• File reading and writing in Java.

However, we will learn each single module of this File handling problem. Here’s the step by step solution to develop the program and How to write to a file in Java –

Major Steps :

[Step 1] Prepare any text file having some text (fileRead.txt in this case).

[Step 2] Use any Reader class to Read text from File (BufferedReader in this case).

[Step 3] After reading file, pass its text/string to a Writer class object (like BufferedWriter class).

[Step 4] Setup the path & filename, then create & write in some text in (writeFile.txt file in this case).

[Step 5] Go to the directory/folder and verify the output/result.

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Solution : Java program to Read a Text file and Write to another File

A solution to this File Input/Output problem –

package com.shubhamklogic.core.java.concepts;

import java.io.FileReader;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.File;

public class FileReadWrite {

    public static void main(String[] args) {                      // Explaining : Step-by-Step ...

        // Calling a custom method 'readAllCharacters' to read all the text 
        // In given file name 'fileRead.txt'
        String fullText = readAllCharacters("fileRead.txt");


        // Calling another custom method to write text in file 'fileWrite.txt'
        // that we fetched above
        writeAllCharacters(fullText, "fileWrite.txt");

    }


    // Our method to Read text from a File 
    // And return that text to the invoker method ( 'main()' in this case )
    public static String readAllCharacters(String fileName) {


        // Using 'StringBuffer' class to repeatedly concatenate the Text (String)
        StringBuffer fullText = new StringBuffer();
        try {


            // Preparing a complete path to the file, from where we will read its Text
            String fileNameWithPath =
                "C:\\Users\\shubham\\Desktop\\shubhamklogic\\java\\" + fileName;


            // Creating a 'File' object
            File file = new File(fileNameWithPath);


            // Creating an object of 'BufferedReader' class, to manage the file
            BufferedReader br = new BufferedReader(new FileReader(file));


            // OPTIONAL STATEMENT: It's just for Logging Purpose, to tell you- What's going on?
            System.out.println("[INFO] 1: BufferedReader Object Created...");


            // Here, We created an String object 'textInLine' to read each single line in file,
            // Then, We ran a while loop until we reach at the end of file,
            // Technically speaking, running the loop untill got the 'null' value
            String textInLine = "";
            while ((textInLine = br.readLine()) != null)
                fullText.append(textInLine);

            System.out.println("[INFO] 2: File Read Successfully...");

        } catch (Exception e) {

            System.out.println("[INFO] 2.1: Hey, Exception occured! \n" + e.getMessage());

        } finally {

            // We read the whole file, 
            // Now returning the 'fullText' to write in other file...
            return fullText.toString();
        }

    }


    // Method will write the text in a file
    public static void writeAllCharacters(String fullText, String fileName) {

        try {

            // Preparing a complete path to the file, to where we will write text
            String fileNameWithPath =
                         "C:\\Users\\shubham\\Desktop\\shubhamklogic\\java\\" + fileName;


            // Created a 'BufferedWriter' object,
            // It contains methods to write text into a File ...
            BufferedWriter writer = new BufferedWriter(new FileWriter(fileNameWithPath));


            // Writing 'fullText'
            writer.write(fullText);


            // close() method flushes the characters from the buffer stream 
            // and then close it
            writer.close();

            System.out.println("[INFO] 4: BufferedReader closed.");

            // OPTIONAL STATEMENT: Just to let you know, What's going on?
            System.out.println("[INFO] 3: File Written Successfully...");

        } catch (Exception e) {
    
            // Catch mechanism : To handle some exceptional situations
            System.out.println("[INFO]3.1: Hey, Exception occured! \n" + e.getMessage());
        }
    }
} // Closing 'FileReadWrite' Java Class...

 

Output : When you’ll run the above program, you’ll successfully get the following output –

[INFO] 1: BufferedReader Object Created...
[INFO] 2: File Read Successfully...
[INFO] 4: BufferedReader closed.
[INFO] 3: File Written Successfully...

 

The Screenshot :

And here is the screenshot, after running the above Java File I/O program –

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Wrap Up 

So far, we have learned to develop a Java program to read a Text File and write to another File. For simplicity, I have simply break down this program into two modules. You can also, try it yourself as –

1)  A program to read data from File in Java, and
2) Write a Java program to write into a Text file,

I hope, this article helped you to learn a bit more about Java. If you have any doubt or query, then do comment or send me a mail via Google, I’ll try my best to give you a solution.

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