public class ByteUtil {

   
    public static void main(String[] args) {
        short s = -20;
        byte[] b = new byte[2];
        putShort(b, s, 0);
        ByteBuffer buf = ByteBuffer.allocate(2);
        buf.put(b);
        buf.flip();
        System.out.println(getShort(b, 0));
        System.out.println(buf.getShort());
        System.out.println("***************************");
        int i = -40;
        b = new byte[4];
        putInt(b, i, 0);
        buf = ByteBuffer.allocate(4);
        buf.put(b);
        buf.flip();
        System.out.println(getInt(b, 0));
        System.out.println(buf.getInt());
        System.out.println("***************************");
        long l = -40;
        b = new byte[8];
        putLong(b, l, 0);
        buf = ByteBuffer.allocate(8);
        buf.put(b);
        buf.flip();
        System.out.println(getLong(b, 0));
        System.out.println(buf.getLong());
        System.out.println("***************************");
    }

    public static void putShort(byte b[], short s, int index) {
        b[index] = (byte) (s >> 8);
        b[index + 1] = (byte) (s >> 0);
    }

    public static short getShort(byte[] b, int index) {
        return (short) (((b[index] << 8) | b[index + 1] & 0xff));
    }

    // ///////////////////////////////////////////////////////
    public static void putInt(byte[] bb, int x, int index) {
        bb[index + 0] = (byte) (x >> 24);
        bb[index + 1] = (byte) (x >> 16);
        bb[index + 2] = (byte) (x >> 8);
        bb[index + 3] = (byte) (x >> 0);
    }

    public static int getInt(byte[] bb, int index) {
        return (int) ((((bb[index + 0] & 0xff) << 24)
                | ((bb[index + 1] & 0xff) << 16)
                | ((bb[index + 2] & 0xff) << 8) | ((bb[index + 3] & 0xff) << 0)));
    }

    // /////////////////////////////////////////////////////////
    public static void putLong(byte[] bb, long x, int index) {
        bb[index + 0] = (byte) (x >> 56);
        bb[index + 1] = (byte) (x >> 48);
        bb[index + 2] = (byte) (x >> 40);
        bb[index + 3] = (byte) (x >> 32);
        bb[index + 4] = (byte) (x >> 24);
        bb[index + 5] = (byte) (x >> 16);
        bb[index + 6] = (byte) (x >> 8);
        bb[index + 7] = (byte) (x >> 0);
    }

    public static long getLong(byte[] bb, int index) {
        return ((((long) bb[index + 0] & 0xff) << 56)
                | (((long) bb[index + 1] & 0xff) << 48)
                | (((long) bb[index + 2] & 0xff) << 40)
                | (((long) bb[index + 3] & 0xff) << 32)
                | (((long) bb[index + 4] & 0xff) << 24)
                | (((long) bb[index + 5] & 0xff) << 16)
                | (((long) bb[index + 6] & 0xff) << 8) | (((long) bb[index + 7] & 0xff) << 0));
    }