public class NumberUtil {
    /**
     * int整數轉換為4位元組的byte陣列
     * 
     * @param i
     *            整數
     * @return byte陣列
     */
    public static byte[] intToByte4(int i) {
        byte[] targets = new byte[4];
        targets[3] = (byte) (i & 0xFF);
        targets[2] = (byte) (i >> 8
 
 & 0xFF);
        targets[1] = (byte) (i >> 16 & 0xFF);
        targets[0] = (byte) (i >> 24 & 0xFF);
        return targets;
    }

    /**
     * long整數轉換為8位元組的byte陣列
     * 
     * @param lo
     *            long整數
     * @return byte陣列
     */
    public static byte[] longToByte8
 
(long lo) {
        byte[] targets = new byte[8];
        for (int i = 0; i < 8; i++) {
            int offset = (targets.length - 1 - i) * 8;
            targets[i] = (byte) ((lo >>> offset) & 0xFF);
        }
        return targets;
    }

    /**
     * short整數轉換為2位元組的byte陣列
     * 
     * @param
 
 s
     *            short整數
     * @return byte陣列
     */
    public static byte[] unsignedShortToByte2(int s) {
        byte[] targets = new byte[2];
        targets[0] = (byte) (s >> 8 & 0xFF);
        targets[1] = (byte) (s & 0xFF);
        return targets;
    }

    /**
     * byte陣列轉換為無符號short整數
     * 
     * @param bytes
     *            byte陣列
     * @return short整數
     */
    public static int byte2ToUnsignedShort(byte[] bytes) {
        return byte2ToUnsignedShort(bytes, 0);
    }

    /**
     * byte陣列轉換為無符號short整數
     * 
     * @param bytes
     *            byte陣列
     * @param off
     *            開始位置
     * @return short整數
     */
    public static int byte2ToUnsignedShort(byte[] bytes, int off) {
        int high = bytes[off];
        int low = bytes[off + 1];
        return (high << 8 & 0xFF00) | (low & 0xFF);
    }

    /**
     * byte陣列轉換為int整數
     * 
     * @param bytes
     *            byte陣列
     * @param off
     *            開始位置
     * @return int整數
     */
    public static int byte4ToInt(byte[] bytes, int off) {
        int b0 = bytes[off] & 0xFF;
        int b1 = bytes[off + 1] & 0xFF;
        int b2 = bytes[off + 2] & 0xFF;
        int b3 = bytes[off + 3] & 0xFF;
        return (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
    }
}