How to read and write binary files in Java?

What is a binary file?

A binary file is a computer file that is not a text file. The term "binary file" is often used as a term meaning "non-text file". Many binary file formats contain parts that can be interpreted as text

Methods for reading a binary file:

Reading and Writing Binary Files Using FileInputStream and FileOutputStream:

The following examples use the FileInputStream and FileOutputStream classes to perform low level binary I/O.

Example:

import java.io.*;

class Main {
    public static void main (String[] args) throws IOException {

        String fileName="out.bin";
        FileOutputStream fileOutputStream=new FileOutputStream(fileName);
        ObjectOutputStream objectOutputStream=new           ObjectOutputStream(fileOutputStream);
        objectOutputStream.writeInt(2000);
        objectOutputStream.writeInt(3000);
        objectOutputStream.writeInt(4000);
        objectOutputStream.close();
        System.out.println("Done Writing");
        FileInputStream fileInputStream=new FileInputStream(fileName);
        ObjectInputStream objectInputStream=new ObjectInputStream(fileInputStream);
        System.out.println(objectInputStream.readInt());
        System.out.println(objectInputStream.readInt());
        System.out.println(objectInputStream.readInt());
        System.out.println("Done Reading");
        objectInputStream.close();

    }
}

Output:

Done Writing
2000
3000
4000
Done Reading

Reading and Writing Binary Files Using BufferedInputStream and BufferedOutputStream:

The following examples use the BufferedInputStream and BufferedOutputStream classes to perform low level binary I/O:

Using BufferedInputStream and BufferedOutputStream is as same as FileInputStream and FileOutputStream. The only difference is that a buffered stream uses an array of byte internally to buffer the input nd output to reduce the number of calls to the native API, hence increasing IO performance.

By default, both BufferedInputStream and BufferedOutputStream has an internal buffer of 8192 bytes (8KB), but we can specify a custom buffer size at initialization

Example:

import java.io.*;

class Main {
    public static void main (String[] args) throws IOException {

        String fileName="out.bin";
        BufferedOutputStream bufferedOutputStream=new BufferedOutputStream(new FileOutputStream(fileName));
        bufferedOutputStream.write(2000);
        bufferedOutputStream.write(3000);
        bufferedOutputStream.write(4000);
        bufferedOutputStream.close();
        System.out.println("Done Writing");
        BufferedInputStream bufferedInputStream=new BufferedInputStream(new FileInputStream(fileName));
        System.out.println(bufferedInputStream.read());
        System.out.println(bufferedInputStream.read());
        System.out.println(bufferedInputStream.read());
        System.out.println("Done Reading");
        bufferedOutputStream.close();

    }
}

Output:

Done Writing
208
184
160
Done Reading

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