你真正理解java的字符类型了吗？（bit，byte，short，int等字符类型）

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);
	}
}