java byte数组与int，long，short，byte转换

 public class DataTypeChangeHelper {
     /**
      * 将一个单字节的byte转换成32位的int
      *
      * @param b
      *            byte
      * @return convert result
      */
     public static int unsignedByteToInt(byte b) {
         return (int) b & 0xFF;
     }

     /**
      * 将一个单字节的Byte转换成十六进制的数
      *
      * @param b
      *            byte
      * @return convert result
      */
     public static String byteToHex(byte b) {
         int i = b & 0xFF;
         return Integer.toHexString(i);
     }

     /**
      * 将一个4byte的数组转换成32位的int
      *
      * @param buf
      *            bytes buffer
      * @param byte[]中开始转换的位置
      * @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;
     }

     /**
      * 将16位的short转换成byte数组
      *
      * @param s
      *            short
      * @return byte[] 长度为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;
     }

     /**
      * 将32位整数转换成长度为4的byte数组
      *
      * @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转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,无符号右移。
         return targets;
     }

     /**
      * 将长度为2的byte数组转换为16位int
      *
      * @param res
      *            byte[]
      * @return int
      * */
     public static int byte2int(byte[] res) {
         // res = InversionByte(res);
         // 一个byte数据左移24位变成0x??000000，再右移8位变成0x00??0000
         int targets = (res[0] & 0xff) | ((res[1] << 8) & 0xff00); // | 表示安位或
         return targets;
     }
 }