[转载] java中byte数组与int，long，short间的转换

文章转载自http://blog.csdn.net/leetcworks/article/details/7390731

 package com.util;
 
 /**
  *
  * <ul>
  * <li>文件名称: com.born.util.ByteUtil.java</li>
  * <li>文件描述: byte转换工具</li>
  * <li>版权所有: 版权所有(C)2001-2006</li>
  * <li>公 司: bran</li>
  * <li>内容摘要:</li>
  * <li>其他说明:</li>
  * <li>完成日期：2011-7-18</li>
  * <li>修改记录0：无</li>
  * </ul>
  *
  * @version 1.0
  * @author 许力多
  */
 public class ByteUtil {
     /**
      * 转换short为byte
      *
      * @param b
      * @param s
      *            需要转换的short
      * @param index
      */
     public static void putShort(byte b[], short s, int index) {
         b[index + 1] = (byte) (s >> 8);
         b[index + 0] = (byte) (s >> 0);
     }
 
     /**
      * 通过byte数组取到short
      *
      * @param b
      * @param index
      *            第几位开始取
      * @return
      */
     public static short getShort(byte[] b, int index) {
         return (short) (((b[index + 1] << 8) | b[index + 0] & 0xff));
     }
 
     /**
      * 转换int为byte数组
      *
      * @param bb
      * @param x
      * @param index
      */
     public static void putInt(byte[] bb, int x, int index) {
         bb[index + 3] = (byte) (x >> 24);
         bb[index + 2] = (byte) (x >> 16);
         bb[index + 1] = (byte) (x >> 8);
         bb[index + 0] = (byte) (x >> 0);
     }
 
     /**
      * 通过byte数组取到int
      *
      * @param bb
      * @param index
      *            第几位开始
      * @return
      */
     public static int getInt(byte[] bb, int index) {
         return (int) ((((bb[index + 3] & 0xff) << 24)
                 | ((bb[index + 2] & 0xff) << 16)
                 | ((bb[index + 1] & 0xff) << 8) | ((bb[index + 0] & 0xff) << 0)));
     }
 
     /**
      * 转换long型为byte数组
      *
      * @param bb
      * @param x
      * @param index
      */
     public static void putLong(byte[] bb, long x, int index) {
         bb[index + 7] = (byte) (x >> 56);
         bb[index + 6] = (byte) (x >> 48);
         bb[index + 5] = (byte) (x >> 40);
         bb[index + 4] = (byte) (x >> 32);
         bb[index + 3] = (byte) (x >> 24);
         bb[index + 2] = (byte) (x >> 16);
         bb[index + 1] = (byte) (x >> 8);
         bb[index + 0] = (byte) (x >> 0);
     }
 
     /**
      * 通过byte数组取到long
      *
      * @param bb
      * @param index
      * @return
      */
     public static long getLong(byte[] bb, int index) {
         return ((((long) bb[index + 7] & 0xff) << 56)
                 | (((long) bb[index + 6] & 0xff) << 48)
                 | (((long) bb[index + 5] & 0xff) << 40)
                 | (((long) bb[index + 4] & 0xff) << 32)
                 | (((long) bb[index + 3] & 0xff) << 24)
                 | (((long) bb[index + 2] & 0xff) << 16)
                 | (((long) bb[index + 1] & 0xff) << 8) | (((long) bb[index + 0] & 0xff) << 0));
     }
 
     /**
      * 字符到字节转换
      *
      * @param ch
      * @return
      */
     public static void putChar(byte[] bb, char ch, int index) {
         int temp = (int) ch;
         // byte[] b = new byte[2];
         for (int i = 0; i < 2; i ++ ) {
             bb[index + i] = new Integer(temp & 0xff).byteValue(); // 将最高位保存在最低位
             temp = temp >> 8; // 向右移8位
         }
     }
 
     /**
      * 字节到字符转换
      *
      * @param b
      * @return
      */
     public static char getChar(byte[] b, int index) {
         int s = 0;
         if (b[index + 1] > 0)
             s += b[index + 1];
         else
             s += 256 + b[index + 0];
         s *= 256;
         if (b[index + 0] > 0)
             s += b[index + 1];
         else
             s += 256 + b[index + 0];
         char ch = (char) s;
         return ch;
     }
 
     /**
      * float转换byte
      *
      * @param bb
      * @param x
      * @param index
      */
     public static void putFloat(byte[] bb, float x, int index) {
         // byte[] b = new byte[4];
         int l = Float.floatToIntBits(x);
         for (int i = 0; i < 4; i++) {
             bb[index + i] = new Integer(l).byteValue();
             l = l >> 8;
         }
     }
 
     /**
      * 通过byte数组取得float
      *
      * @param bb
      * @param index
      * @return
      */
     public static float getFloat(byte[] b, int index) {
         int l;
         l = b[index + 0];
         l &= 0xff;
         l |= ((long) b[index + 1] << 8);
         l &= 0xffff;
         l |= ((long) b[index + 2] << 16);
         l &= 0xffffff;
         l |= ((long) b[index + 3] << 24);
         return Float.intBitsToFloat(l);
     }
 
     /**
      * double转换byte
      *
      * @param bb
      * @param x
      * @param index
      */
     public static void putDouble(byte[] bb, double x, int index) {
         // byte[] b = new byte[8];
         long l = Double.doubleToLongBits(x);
         for (int i = 0; i < 4; i++) {
             bb[index + i] = new Long(l).byteValue();
             l = l >> 8;
         }
     }
 
     /**
      * 通过byte数组取得float
      *
      * @param bb
      * @param index
      * @return
      */
     public static double getDouble(byte[] b, int index) {
         long l;
         l = b[0];
         l &= 0xff;
         l |= ((long) b[1] << 8);
         l &= 0xffff;
         l |= ((long) b[2] << 16);
         l &= 0xffffff;
         l |= ((long) b[3] << 24);
         l &= 0xffffffffl;
         l |= ((long) b[4] << 32);
         l &= 0xffffffffffl;
         l |= ((long) b[5] << 40);
         l &= 0xffffffffffffl;
         l |= ((long) b[6] << 48);
         l &= 0xffffffffffffffl;
         l |= ((long) b[7] << 56);
         return Double.longBitsToDouble(l);
     }
 }

 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;
     }
 }