java中byte数组与int，long，short间的转换

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);
    }
}