java byte数组与int，long，short，byte转换
这两天碰到的小问题，给初学者一点帮助吧。[*]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));
[*] secondByte = (0x000000FF & ((int) buf));
[*] thirdByte = (0x000000FF & ((int) buf));
[*] fourthByte = (0x000000FF & ((int) buf));
[*] 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;
[*] for (int i = 0; i < 2; i++) {
[*] int offset = (targets.length - 1 - i) * 8;
[*] targets = (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;
[*] for (int i = 0; i < 4; i++) {
[*] int offset = (targets.length - 1 - i) * 8;
[*] targets = (byte) ((s >>> offset) & 0xff);
[*] }
[*] return targets;
[*] }
[*]
[*] /**
[*] * long to byte[]
[*] *
[*] * @param s
[*] * long
[*] * @return byte[]
[*] * */
[*] public static byte[] longToByteArray(long s) {
[*] byte[] targets = new byte;
[*] for (int i = 0; i < 8; i++) {
[*] int offset = (targets.length - 1 - i) * 8;
[*] targets = (byte) ((s >>> offset) & 0xff);
[*] }
[*] return targets;
[*] }
[*]
[*] /**32位int转byte[]*/
[*] public static byte[] int2byte(int res) {
[*] byte[] targets = new byte;
[*] targets = (byte) (res & 0xff);// 最低位
[*] targets = (byte) ((res >> 8) & 0xff);// 次低位
[*] targets = (byte) ((res >> 16) & 0xff);// 次高位
[*] targets = (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 & 0xff) | ((res << 8) & 0xff00); // | 表示安位或
[*] return targets;
[*] }
[*]}
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