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;

    }

}