Home » Core Java » io » FileInputStream » Read file in byte array with FileInputStream

About Byron Kiourtzoglou

Byron Kiourtzoglou
Byron is a master software engineer working in the IT and Telecom domains. He is an applications developer in a wide variety of applications/services. He is currently acting as the team leader and technical architect for a proprietary service creation and integration platform for both the IT and Telecom industries in addition to a in-house big data real-time analytics solution. He is always fascinated by SOA, middleware services and mobile development. Byron is co-founder and Executive Editor at Java Code Geeks.

Read file in byte array with FileInputStream

This is an example of how to read a File in a byte array using a FileInputStream. The FileInputStream obtains input bytes from a file in a file system. Reading a file in a byte array with a FileInputStream implies that you should:

  • Create a new File instance by converting the given pathname string into an abstract pathname.
  • Create a FileInputStream by opening a connection to an actual file, the file named by the path name name in the file system.
  • Create a byte array with size equal to the file length.
  • Use read(byte[] b) API method of FileInputStream to read up to certain bytes of data from this input stream into the byte array.
  • Create a String from the byte array.
  • Don’t forget to close the FileInputStream, using the close() API method.

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.core;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

public class ReadFileInByteArrayWithFileInputStream {
	public static void main(String[] args) {
		File file = new File("inputfile.txt");
		FileInputStream fin = null;
		try {
			// create FileInputStream object
			fin = new FileInputStream(file);

			byte fileContent[] = new byte[(int)file.length()];
			// Reads up to certain bytes of data from this input stream into an array of bytes.
			//create string from byte array
			String s = new String(fileContent);
			System.out.println("File content: " + s);
		catch (FileNotFoundException e) {
			System.out.println("File not found" + e);
		catch (IOException ioe) {
			System.out.println("Exception while reading file " + ioe);
		finally {
			// close the streams using close method
			try {
				if (fin != null) {
			catch (IOException ioe) {
				System.out.println("Error while closing stream: " + ioe);

This was an example of how to read a file in a byte array with a FileInputStream in Java.

Do you want to know how to develop your skillset to become a Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you our best selling eBooks for FREE!


1. JPA Mini Book

2. JVM Troubleshooting Guide

3. JUnit Tutorial for Unit Testing

4. Java Annotations Tutorial

5. Java Interview Questions

6. Spring Interview Questions

7. Android UI Design


and many more ....



Want to take your Java Skills to the next level?
Grab our programming books for FREE!
  • Save time by leveraging our field-tested solutions to common problems.
  • The books cover a wide range of topics, from JPA and JUnit, to JMeter and Android.
  • Each book comes as a standalone guide (with source code provided), so that you use it as reference.
Last Step ...

Where should we send the free eBooks?

Good Work!
To download the books, please verify your email address by following the instructions found on the email we just sent you.