[java] Convert integer into byte array (Java)

what's a fast way to convert an Integer into a Byte Array?

e.g. 0xAABBCCDD => {AA, BB, CC, DD}

It's my solution:

public void getBytes(int val) {
    byte[] bytes = new byte[Integer.BYTES];
    for (int i = 0;i < bytes.length; i ++) {
        int j = val % Byte.MAX_VALUE;
        bytes[i] = (j == 0 ? Byte.MAX_VALUE : j);
    }
}

Also Stringy method:

public void getBytes(int val) {
    String hex = Integer.toHexString(val);
    byte[] val = new byte[hex.length()/2]; // because byte is 2 hex chars
    for (int i = 0; i < hex.length(); i+=2)
        val[i] = Byte.parseByte("0x" + hex.substring(i, i+2), 16);
    return val;
}

Using BigInteger:

private byte[] bigIntToByteArray( final int i ) {
    BigInteger bigInt = BigInteger.valueOf(i);      
    return bigInt.toByteArray();
}

Using DataOutputStream:

private byte[] intToByteArray ( final int i ) throws IOException {      
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    DataOutputStream dos = new DataOutputStream(bos);
    dos.writeInt(i);
    dos.flush();
    return bos.toByteArray();
}

Using ByteBuffer:

public byte[] intToBytes( final int i ) {
    ByteBuffer bb = ByteBuffer.allocate(4); 
    bb.putInt(i); 
    return bb.array();
}

Simple solution which properly handles ByteOrder:

ByteBuffer.allocate(4).order(ByteOrder.nativeOrder()).putInt(yourInt).array();

use this function it works for me

public byte[] toByteArray(int value) {
    return new byte[] {
            (byte)(value >> 24),
            (byte)(value >> 16),
            (byte)(value >> 8),
            (byte)value};
}

it translates the int into a byte value

You can use BigInteger:

From Integers:

byte[] array = BigInteger.valueOf(0xAABBCCDD).toByteArray();
System.out.println(Arrays.toString(array))
// --> {-86, -69, -52, -35 }

The returned array is of the size that is needed to represent the number, so it could be of size 1, to represent 1 for example. However, the size cannot be more than four bytes if an int is passed.

From Strings:

BigInteger v = new BigInteger("AABBCCDD", 16);
byte[] array = v.toByteArray();

However, you will need to watch out, if the first byte is higher 0x7F (as is in this case), where BigInteger would insert a 0x00 byte to the beginning of the array. This is needed to distinguish between positive and negative values.

If you like Guava, you may use its Ints class:

For int ? byte[], use toByteArray():

byte[] byteArray = Ints.toByteArray(0xAABBCCDD);

Result is {0xAA, 0xBB, 0xCC, 0xDD}.

Its reverse is fromByteArray() or fromBytes():

int intValue = Ints.fromByteArray(new byte[]{(byte) 0xAA, (byte) 0xBB, (byte) 0xCC, (byte) 0xDD});
int intValue = Ints.fromBytes((byte) 0xAA, (byte) 0xBB, (byte) 0xCC, (byte) 0xDD);

Result is 0xAABBCCDD.

Can also shift -

byte[] ba = new byte[4];
int val = Integer.MAX_VALUE;

for(byte i=0;i<4;i++)
    ba[i] = (byte)(val >> i*8);
    //ba[3-i] = (byte)(val >> i*8); //Big-endian

Here's a method that should do the job just right.

public byte[] toByteArray(int value)
{
    final byte[] destination = new byte[Integer.BYTES];
    for(int index = Integer.BYTES - 1; index >= 0; index--)
    {
        destination[i] = (byte) value;
        value = value >> 8;
    };
    return destination;
};

very easy with android

int i=10000;
byte b1=(byte)Color.alpha(i);
byte b2=(byte)Color.red(i);
byte b3=(byte)Color.green(i);
byte b4=(byte)Color.blue(i);

This will help you.

import java.nio.ByteBuffer;
import java.util.Arrays;

public class MyClass
{
    public static void main(String args[]) {
        byte [] hbhbytes = ByteBuffer.allocate(4).putInt(16666666).array();

        System.out.println(Arrays.toString(hbhbytes));
    }
}