Javaはbyte[]とintを互いに変換する

    /**
     *       byte       
     */
    private static byte[] intToBytes(int a, int length) {
        byte[] bs = new byte[length];
        for (int i = bs.length - 1; i >= 0; i--) {
            bs[i] = (byte) (a % 0xFF);
            a = a / 0xFF;
        }
        return bs;
    }

    /**
     *  byte       
     */
    private static int bytesToInt(byte[] bs) {
        int a = 0;
        for (int i = bs.length - 1; i >= 0; i--) {
            a += bs[i] * Math.pow(0xFF, bs.length - i - 1);
        }
        return a;
    }