Java - Convert int to Byte Array of 4 Bytes? [duplicate]

问题

Possible Duplicate:
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.

回答1:

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.

回答2:

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();
}

回答3:

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.

回答4:

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

来源：https://stackoverflow.com/questions/6374915/java-convert-int-to-byte-array-of-4-bytes

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