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Java Write to File - 4 Ways to Write File in Java

Published on August 3, 2022
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By Pankaj
Developer and author at DigitalOcean.
Java Write to File - 4 Ways to Write File in Java

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Java provides several ways to write to file. We can use FileWriter, BufferedWriter, java 7 Files and FileOutputStream to write a file in Java.

Java Write to File

java write to file, write file in java Let’s have a brief look at four options we have for java write to file operation.

  1. FileWriter: FileWriter is the simplest way to write a file in Java. It provides overloaded write method to write int, byte array, and String to the File. You can also write part of the String or byte array using FileWriter. FileWriter writes directly into Files and should be used only when the number of writes is less.
  2. BufferedWriter: BufferedWriter is almost similar to FileWriter but it uses internal buffer to write data into File. So if the number of write operations is more, the actual IO operations are less and performance is better. You should use BufferedWriter when the number of write operations is more.
  3. FileOutputStream: FileWriter and BufferedWriter are meant to write text to the file but when you need raw stream data to be written into file, you should use FileOutputStream to write file in java.
  4. Files: Java 7 introduced Files utility class and we can write a file using its write function. Internally it’s using OutputStream to write byte array into file.

Java Write to File Example

Here is the example showing how we can write a file in java using FileWriter, BufferedWriter, FileOutputStream, and Files in java. WriteFile.java

package com.journaldev.files;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Paths;

public class WriteFile {

    /**
     * This class shows how to write file in java
     * @param args
     * @throws IOException 
     */
    public static void main(String[] args) {
        String data = "I will write this String to File in Java";
        int noOfLines = 10000;
        writeUsingFileWriter(data);
        
        writeUsingBufferedWriter(data, noOfLines);
        
        writeUsingFiles(data);
        
        writeUsingOutputStream(data);
        System.out.println("DONE");
    }

    /**
     * Use Streams when you are dealing with raw data
     * @param data
     */
    private static void writeUsingOutputStream(String data) {
        OutputStream os = null;
        try {
            os = new FileOutputStream(new File("/Users/pankaj/os.txt"));
            os.write(data.getBytes(), 0, data.length());
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            try {
                os.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    
    /**
     * Use Files class from Java 1.7 to write files, internally uses OutputStream
     * @param data
     */
    private static void writeUsingFiles(String data) {
        try {
            Files.write(Paths.get("/Users/pankaj/files.txt"), data.getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * Use BufferedWriter when number of write operations are more
     * It uses internal buffer to reduce real IO operations and saves time
     * @param data
     * @param noOfLines
     */
    private static void writeUsingBufferedWriter(String data, int noOfLines) {
        File file = new File("/Users/pankaj/BufferedWriter.txt");
        FileWriter fr = null;
        BufferedWriter br = null;
        String dataWithNewLine=data+System.getProperty("line.separator");
        try{
            fr = new FileWriter(file);
            br = new BufferedWriter(fr);
            for(int i = noOfLines; i>0; i--){
                br.write(dataWithNewLine);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            try {
                br.close();
                fr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * Use FileWriter when number of write operations are less
     * @param data
     */
    private static void writeUsingFileWriter(String data) {
        File file = new File("/Users/pankaj/FileWriter.txt");
        FileWriter fr = null;
        try {
            fr = new FileWriter(file);
            fr.write(data);
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            //close resources
            try {
                fr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

These are the standard methods to write a file in java and you should choose any one of these based on your project requirements. That’s all for Java write to file example.

You can checkout more Java IO examples from our GitHub Repository.

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About the authors
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Pankaj

author

Developer and author at DigitalOcean.

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Was this helpful?

if path is not available, will it create the directory and filename with extension. whatever we mentioned in path.get() ?

- stephen

    This would be better to show try-with-resources, as in: try (BufferedWriter br = new BufferedWriter(new FileWriter(file))) { } catch (Exception e) { } // No finally

    - Steve Waring

      You have to use the E!

      - Ur Friend

        I copies the code and put in a text file renaming it with filename being classname and extension .java. When compiling, I am getting this error. What could be the reason. Error: Could not find or load main class *.java Caused by: java.lang.ClassNotFoundException: *.java

        - UNNIKRISHNAN CHANDUVARATH

          how can I write in the next line using writeusingfilewriter? I know if I add true in (file) I can save any new value, but, how can I do the previous step?

          - Jaffet

            Hello, Can we store real time output into a text file. I mean that, i am working on NMEA data and this data is continuously coming from GPS device in my computer through USB port, but i am not storing this data into a text file. can we store this real continuous output into a text file in java.

            - Neeraj Jain

              explained nice!! but when i try to write some data in file it delete previous data…what should i do if i want to keep previous data…

              - Anang

                Hi… How can i copy/write the result from the SQLquery of the data base, which is in the form of list (List objList = DBRepositories.getME1Object(dbSession, “H612O2GN” )), in to the file??? Please reply…

                - Danish Nomani

                  nice tutorial but is it possible to do simultaneous read and write on same file in java ?

                  - wasim