java byte数组与int,long,short,byte的转换实现方法

实例如下：

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;
 }
}