자바 바이트 데이터 형식 변환

    ：http://www.cnblogs.com/xyqCreator/archive/2012/06/13/2547657.html

public class DataTypeChangeHelper {
	/**
	 *        byte   32  int
	 * 
	 * @param b
	 *            byte
	 * @return convert result
	 */
	public static int unsignedByteToInt(byte b) {
		return (int) b & 0xFF;
	}

	/**
	 *        Byte         
	 * 
	 * @param b
	 *            byte
	 * @return convert result
	 */
	public static String byteToHex(byte b) {
		int i = b & 0xFF;
		return Integer.toHexString(i);
	}

	/**
	 *    4byte      32  int
	 * 
	 * @param buf
	 *            bytes buffer
	 * @param byte[]        
	 * @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;
	}

	/**
	 *  16  short   byte  
	 * 
	 * @param s
	 *            short
	 * @return byte[]    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;
	}

	/**
	 *  32         4 byte  
	 * 
	 * @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 int byte[] */
	public static byte[] int2byte(int res) {
		byte[] targets = new byte[4];
		targets[0] = (byte) (res & 0xff);//    
		targets[1] = (byte) ((res >> 8) & 0xff);//    
		targets[2] = (byte) ((res >> 16) & 0xff);//    
		targets[3] = (byte) (res >>> 24);//    ,     。
		return targets;
	}

	/**
	 *     2 byte     16 int
	 * 
	 * @param res
	 *            byte[]
	 * @return int
	 * */
	public static int byte2int(byte[] res) {
		// res = InversionByte(res);
		//   byte    24   0x??000000，   8   0x00??0000
		int targets = (res[0] & 0xff) | ((res[1] << 8) & 0xff00); // |      
		return targets;
	}
}