java中byte数组与int，long，short间的转换

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;
}
}