Convert InputStream to byte array in Java

This post will discuss how to convert InputStream to byte array in Java.

1. Using `java.io.ByteArrayOutputStream`

The idea is to read each byte from the specified InputStream and write it to a ByteArrayOutputStream, then call toByteArray() to get the current contents of this output stream as a byte array. Since the total number of bytes to be read is unknown, we have allocated the buffer of size 1024.

import java.io.ByteArrayInputStream;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.nio.charset.StandardCharsets;

// Convert `InputStream` to byte array in Java

class Main

{

public static byte[] toByteArray(InputStream in) throws IOException

{

ByteArrayOutputStream os = new ByteArrayOutputStream();

byte[] buffer = new byte[1024];

int len;

// read bytes from the input stream and store them in the buffer

while ((len = in.read(buffer)) != -1)

{

// write bytes from the buffer into the output stream

os.write(buffer, 0, len);

}

return os.toByteArray();

}

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

{

// input stream

InputStream in = new ByteArrayInputStream("Techie Delight"

.getBytes(StandardCharsets.UTF_8));

// byte array

byte[] bytes = toByteArray(in);

System.out.println(new String(bytes));

}

Download Run Code

Output:

Techie Delight

2. Using Guava Library

We can use ByteStreams class from Guava, whose toByteArray() method reads all bytes from an input stream into a byte array.

import com.google.common.io.ByteStreams;

import java.io.ByteArrayInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.nio.charset.StandardCharsets;

// Convert `InputStream` to byte array in Java using Guava

class Main

{

public static byte[] toByteArray(InputStream in) throws IOException

{

byte[] bytes = ByteStreams.toByteArray(in);

return bytes;

}

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

{

// input stream

InputStream in = new ByteArrayInputStream("Techie Delight"

.getBytes(StandardCharsets.UTF_8));

// byte array

byte[] bytes = toByteArray(in);

System.out.println(new String(bytes));

}

Download Code

Output:

Techie Delight

3. Using Apache Commons IO

Like Guava, Apache Commons IO has IOUtils class whose toByteArray() method returns the contents of an InputStream as a byte array.

import org.apache.commons.io.IOUtils;

import java.io.ByteArrayInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.nio.charset.StandardCharsets;

// Convert `InputStream` to byte array in Java using Apache Commons

class Main

{

public static byte[] toByteArray(InputStream in) throws IOException

{

byte[] bytes = IOUtils.toByteArray(in);

return bytes;

}

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

{

// input stream

InputStream in = new ByteArrayInputStream("Techie Delight"

.getBytes(StandardCharsets.UTF_8));

// byte array

byte[] bytes = toByteArray(in);

System.out.println(new String(bytes));

}

Download Code

Output:

Techie Delight

4. Using `sun.misc.IOUtils`

We can also use sun.misc.IOUtils, which is one of Sun’s proprietary Java classes. We should avoid their use as it is not guaranteed to work on all Java-compatible platforms or even in future versions on the same platform.

import sun.misc.IOUtils;

import java.io.ByteArrayInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.nio.charset.StandardCharsets;

// Convert `InputStream` to byte array in Java

class Main

{

public static byte[] toByteArray(InputStream in) throws IOException

{

byte[] bytes = IOUtils.readFully(in, -1, false);

return bytes;

}

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

{

// input stream

InputStream in = new ByteArrayInputStream("Techie Delight"

.getBytes(StandardCharsets.UTF_8));

// byte array

byte[] bytes = toByteArray(in);

System.out.println(new String(bytes));

}

Download Code

Output:

Techie Delight

5. Using Java 9

In Java 9, we can do something like:

public static byte[] toByteArray(InputStream in) throws IOException {

return in.readAllBytes();

}

Or use ByteArrayOutputStream.transferTo() method:

public static byte[] toByteArray(InputStream in) throws IOException

{

ByteArrayOutputStream bos = new ByteArrayOutputStream();

in.transferTo(bos);

return bos.toByteArray();

}

That’s all about converting InputStream to byte array in Java.

Convert InputStream to byte array in Java

1. Using java.io.ByteArrayOutputStream

2. Using Guava Library

3. Using Apache Commons IO

4. Using sun.misc.IOUtils

5. Using Java 9

1. Using `java.io.ByteArrayOutputStream`

4. Using `sun.misc.IOUtils`