Read file in byte array with FileInputStream

Byron KiourtzoglouNovember 11th, 2012Last Updated: October 26th, 2013

0 1,178 1 minute read

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.
            fin.read(fileContent);
            //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) {
                    fin.close();
                }
            }
            catch (IOException ioe) {
                System.out.println("Error while closing stream: " + ioe);
            }
        }
    }
}