java byte數組與int，long，short，byte轉換

public class DataTypeChangeHelper {
    /**
     * 將一個單字節的byte轉換成32位的int
     * 
     * @param b
     *            byte
     * @return convert result
     */
    public static int unsignedByteToInt(byte b) {
        return (int) b & 0xFF;
    }

    /**
     * 將一個單字節的Byte轉換成十六進制的數
     * 
     * @param b
     *            byte
     * @return convert result
     */
    public static String byteToHex(byte b) {
        int i = b & 0xFF;
        return Integer.toHexString(i);
    }

    /**
     * 將一個4byte的數組轉換成32位的int
     * 
     * @param buf
     *            bytes buffer
     * @param byte[]中開始轉換的位置
     * @return convert result
     */
    public static long unsigned4BytesToInt(byte[] buf, int pos) {
        int firstByte = 0;
        int secondByte = 0;
        int thirdByte = 0;
        int fourthByte = 0;
        int index = pos;
        firstByte = (0x000000FF & ((int) buf[index]));
        secondByte = (0x000000FF & ((int) buf[index + 1]));
        thirdByte = (0x000000FF & ((int) buf[index + 2]));
        fourthByte = (0x000000FF & ((int) buf[index + 3]));
        index = index + 4;
        return ((long) (firstByte << 24 | secondByte << 16 | thirdByte << 8 | fourthByte)) & 0xFFFFFFFFL;
    }

    /**
     * 將16位的short轉換成byte數組
     * 
     * @param s
     *            short
     * @return byte[] 長度為2
     * */
    public static byte[] shortToByteArray(short s) {
        byte[] targets = new byte[2];
        for (int i = 0; i < 2; i++) {
            int offset = (targets.length - 1 - i) * 8;
            targets[i] = (byte) ((s >>> offset) & 0xff);
        }
        return targets;
    }

    /**
     * 將32位整數轉換成長度為4的byte數組
     * 
     * @param s
     *            int
     * @return byte[]
     * */
    public static byte[] intToByteArray(int s) {
        byte[] targets = new byte[2];
        for (int i = 0; i < 4; i++) {
            int offset = (targets.length - 1 - i) * 8;
            targets[i] = (byte) ((s >>> offset) & 0xff);
        }
        return targets;
    }

    /**
     * long to byte[]
     * 
     * @param s
     *            long
     * @return byte[]
     * */
    public static byte[] longToByteArray(long s) {
        byte[] targets = new byte[2];
        for (int i = 0; i < 8; i++) {
            int offset = (targets.length - 1 - i) * 8;
            targets[i] = (byte) ((s >>> offset) & 0xff);
        }
        return targets;
    }

    /**32位int轉byte[]*/
    public static byte[] int2byte(int res) {
        byte[] targets = new byte[4];
        targets[0] = (byte) (res & 0xff);// 最低位
        targets[1] = (byte) ((res >> 8) & 0xff);// 次低位
        targets[2] = (byte) ((res >> 16) & 0xff);// 次高位
        targets[3] = (byte) (res >>> 24);// 最高位,無符號右移。
        return targets;
    }

    /**
     * 將長度為2的byte數組轉換為16位int
     * 
     * @param res
     *            byte[]
     * @return int
     * */
    public static int byte2int(byte[] res) {
        // res = InversionByte(res);
        // 一個byte數據左移24位變成0x??000000，再右移8位變成0x00??0000
        int targets = (res[0] & 0xff) | ((res[1] << 8) & 0xff00); // | 表示安位或
        return targets;
    }
}