Java integer to byte array

Question

I got an integer  1695609641  when I use method    String hex   Integer toHexString 1695609641   system out println hex      gives   6510f329   but I want a byte array   byte   bytearray   new byte      byte  0x65   byte 0x10   byte 0xf3   byte 0x29     How can I make this

User · Answer

Because generally you would want to convert this array back to an int at a later point, here are the methods to convert an array of ints into an array of bytes and vice-versa:

public static byte[] convertToByteArray(final int[] pIntArray)
{
    final byte[] array = new byte[pIntArray.length * 4];
    for (int j = 0; j < pIntArray.length; j++)
    {
        final int c = pIntArray[j];
        array[j * 4] = (byte)((c & 0xFF000000) >> 24);
        array[j * 4 + 1] = (byte)((c & 0xFF0000) >> 16);
        array[j * 4 + 2] = (byte)((c & 0xFF00) >> 8);
        array[j * 4 + 3] = (byte)(c & 0xFF);
    }
    return array;
}

public static int[] convertToIntArray(final byte[] pByteArray)
{
    final int[] array = new int[pByteArray.length / 4];
    for (int i = 0; i < array.length; i++)
        array[i] = (((int)(pByteArray[i * 4]) << 24) & 0xFF000000) |
                (((int)(pByteArray[i * 4 + 1]) << 16) & 0xFF0000) |
                (((int)(pByteArray[i * 4 + 2]) << 8) & 0xFF00) |
                ((int)(pByteArray[i * 4 + 3]) & 0xFF);
    return array;
}

Note that because of sign propagation and such, the "& 0xFF..." are needed when converting back to the int.

User · Answer

My try     public static byte   toBytes final int intVal  final int    intArray        if  intArray    null     intArray length    0             return ByteBuffer allocate 4  putInt intVal  array          else           final ByteBuffer bb   ByteBuffer allocate 4    intArray length   4   putInt intVal           for  final int val   intArray                bb putInt val                     return bb array              With it you can do this    byte   fourBytes   toBytes 0x01020304   byte   eightBytes   toBytes 0x01020304  0x05060708     Full class is here   https   gist github com superbob 6548493  it supports initialization from shorts or long  byte   eightBytesAgain   toBytes 0x0102030405060708L

User · Answer

byte   IntToByteArray  int data             byte   result   new byte 4       result 0     byte    data  amp  0xFF000000   gt  gt  24       result 1     byte    data  amp  0x00FF0000   gt  gt  16       result 2     byte    data  amp  0x0000FF00   gt  gt  8       result 3     byte    data  amp  0x000000FF   gt  gt  0       return result

User · Answer

BigInteger valueOf 1695609641  toByteArray

User · Answer

The chunks below work at least for sending an int over UDP   int to byte array   public byte   intToBytes int my int  throws IOException       ByteArrayOutputStream bos   new ByteArrayOutputStream        ObjectOutput out   new ObjectOutputStream bos       out writeInt my int       out close        byte   int bytes   bos toByteArray        bos close        return int bytes      byte array to int   public int bytesToInt byte   int bytes  throws IOException       ByteArrayInputStream bis   new ByteArrayInputStream int bytes       ObjectInputStream ois   new ObjectInputStream bis       int my int   ois readInt        ois close        return my int

User · Answer

public static byte   intToBytes int x  throws IOException       ByteArrayOutputStream bos   new ByteArrayOutputStream        DataOutputStream out   new DataOutputStream bos       out writeInt x       out close        byte   int bytes   bos toByteArray        bos close        return int bytes

User · Answer

How about   public static final byte   intToByteArray int value        return new byte                  byte  value  gt  gt  gt  24                byte  value  gt  gt  gt  16                byte  value  gt  gt  gt  8                byte value       The idea is not mine  I ve taken it from some post on dzone com

User · Answer

integer  amp  0xFF   for the first byte   integer  gt  gt  8   amp  0xFF   for the second and loop etc   writing into a preallocated byte array  A bit messy  unfortunately

User · Answer

Using Guava   byte   bytearray   Ints toByteArray 1695609641

User · Answer

using Java NIO s ByteBuffer is very simple   byte   bytes   ByteBuffer allocate 4  putInt 1695609641  array     for  byte b   bytes       System out format  0x x    b       output    0x65 0x10 0xf3 0x29

User · Answer

The class org apache hadoop hbase util Bytes has a bunch of handy byte   conversion methods  but you might not want to add the whole HBase jar to your project just for this purpose  It s surprising that not only are such method missing AFAIK from the JDK  but also from obvious libs like commons io

User · Answer

byte   conv   new byte 4   conv 3     byte  input  amp  0xff  input  gt  gt   8  conv 2     byte  input  amp  0xff  input  gt  gt   8  conv 1     byte  input  amp  0xff  input  gt  gt   8  conv 0     byte  input

User · Answer

If you re using apache-commons  public static byte   toByteArray int value        byte result     new byte 4       return Conversion intToByteArray value  0  result  0  4

[java] Java integer to byte array

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