ByteUtils

package sort.bing.com;

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.UnsupportedEncodingException;

public class ByteUtils {

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;
}

public static int byte2int(byte[] 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
| ((res[2] << 24) >>> 8) | (res[3] << 24);
return targets;
}

public static byte[] intToByteArray(int i) throws Exception {
ByteArrayOutputStream buf = new ByteArrayOutputStream();
DataOutputStream out = new DataOutputStream(buf);
System.out.println("i:" + i);
out.writeInt(i);
byte[] b = buf.toByteArray();
System.out.println("i:" + b);
out.close();
buf.close();
return b;
}

/**
* 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;
}

/**
* 注释：字节数组到short的转换！
*
* @param b
* @return
*/
public static short byteToShort(byte[] b) {
short s = 0;
short s0 = (short) (b[0] & 0xff);// 最低位
short s1 = (short) (b[1] & 0xff);
s1 <<= 8;
s = (short) (s0 | s1);
return s;
}

/**
* 把byte[]转换成16进制进制字符串
* @param b
* @return
*/
public static String bytes2HexString(byte[] b) {
String ret = "";
for (int i = 0; i < b.length; i++) {
String hex = Integer.toHexString(b[ i ] & 0xFF);
if (hex.length() == 1) {
hex = '0' + hex;
}
ret += hex.toUpperCase();
}
return ret;
}

/**
* byte[]转换成bit
* @param b
* @return
*/
public static String bytesToBits(byte[] bytes) {
StringBuffer sb = new StringBuffer();
for(byte b:bytes){
sb.append(byteToBits(b));
}
return sb.toString();
}

/**
* byte转换成8位bit
* @param b
* @return
*/
public static String byteToBits(byte b) {
int z = b; z |= 256;
String str = Integer.toBinaryString(z);
int len = str.length();
return str.substring(len-8, len);
}

/**
* 计算校验和
* @param bytes
* @return
*/
public static final int calculateCheckSum(byte[] bytes) {
int sum = 0;
for (byte b : bytes) {
sum += (short)b;
}
return sum>65535 ? (sum-65535) : sum;
}

public static void main(String[] args) throws UnsupportedEncodingException {
// String s = "12" ;
// short n = 100;
// byte[] buf = s.getBytes("UTF-8");
// byte[] buf2 = ByteUtils.shortToByteArray(n);
// System.out.println(calculateCheckSum(buf));
// System.out.println(calculateCheckSum(buf2));
// System.out.println(bytes2HexString(buf2));
byte i = -112;
System.out.println(i & 0xff);
}
}