Java - Convert int to Byte Array of 4 Bytes?

Question

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Convert integer into byte array (Java)

I need to store the length of a buffer, in a byte array 4 bytes large.

Pseudo code:

private byte[] convertLengthToByte(byte[] myBuffer)
{
    int length = myBuffer.length;

    byte[] byteLength = new byte[4];

    //here is where I need to convert the int length to a byte array
    byteLength = length.toByteArray;

    return byteLength;
}

What would be the best way of accomplishing this? Keeping in mind I must convert that byte array back to an integer later.

Take a look at this: http://stackoverflow.com/questions/5399798/byte-array-and-int-conversion-in-java — TacB0sS, Jun 03 '12 at 13:44

Waldheinz · Accepted Answer · 2014-01-20T16:19:03.540

145

You can convert yourInt to bytes by using a ByteBuffer like this:

return ByteBuffer.allocate(4).putInt(yourInt).array();

Beware that you might have to think about the byte order when doing so.

edited Jan 20 '14 at 16:19

answered Jun 16 '11 at 16:05

Waldheinz

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This is better (gets the platform ByteOrder): `ByteBuffer.allocate(4).order(ByteOrder.nativeOrder()).putInt(yourInt).array();` – helmy Nov 13 '19 at 17:43
2

If it's better depends on what you want to do with it. It may be a little bit faster, but having the byte order depend on the platform is a no-no when you want to send those bytes over a network or even write to a file. – Waldheinz Nov 14 '19 at 20:29

score 50 · Answer 2 · edited Apr 30 '12 at 10:59

public static  byte[] my_int_to_bb_le(int myInteger){
    return ByteBuffer.allocate(4).order(ByteOrder.LITTLE_ENDIAN).putInt(myInteger).array();
}

public static int my_bb_to_int_le(byte [] byteBarray){
    return ByteBuffer.wrap(byteBarray).order(ByteOrder.LITTLE_ENDIAN).getInt();
}

public static  byte[] my_int_to_bb_be(int myInteger){
    return ByteBuffer.allocate(4).order(ByteOrder.BIG_ENDIAN).putInt(myInteger).array();
}

public static int my_bb_to_int_be(byte [] byteBarray){
    return ByteBuffer.wrap(byteBarray).order(ByteOrder.BIG_ENDIAN).getInt();
}

score 24 · Answer 3 · edited May 23 '17 at 12:26

24

This should work:

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

Code taken from here.

Edit An even simpler solution is given in this thread.

edited May 23 '17 at 12:26

Community

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answered Jun 16 '11 at 16:04

Miki

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you should be aware of order. in that case order is big endian. from the most significant to the least. – Error Jul 07 '16 at 16:45

score 22 · Answer 4 · edited Sep 24 '13 at 20:09

22

int integer = 60;
byte[] bytes = new byte[4];
for (int i = 0; i < 4; i++) {
    bytes[i] = (byte)(integer >>> (i * 8));
}

edited Sep 24 '13 at 20:09

Franco Rondini

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answered Jun 16 '11 at 16:07

Stas Jaro

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Java - Convert int to Byte Array of 4 Bytes?

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