主要是一次发新浪微博，发网址时看到网址被压缩了，才对这个有兴趣，于是查了查，查到这些
和其Java实现的博文
对第一篇博文，留了疑问，主要是觉得于四个得到的压缩地址中取一个，那之前循环计算不是有些浪费计算能力吗？
不多说废话，这里就贴下自己的Java验证实现代码：
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.io.*;
public class ShortUrl{
public static void main(String[] args){
String url = "";
for(String string:ShortText(url)){
print(string);
}
}
public static String[] ShortText(String string){
String key = "XuLiang";//自定义生成MD5加密字符串的混合KEY
String[] chars = new String[]{//要使用生成URL的字符
"a","b","c","d","e","f","g","h",
"i","j","k","l","m","n","o","p",
"q","r","s","t","u","v","w","x",
"y","z", "0","1","2","3","4","5",
"6","7","8","9","A","B","C","D",
"E","F","G","H","I","J","K","L",
"M","N","O","P","Q","R","S","T",
"U","V", "W","X","Y","Z"
};
String hex = MD5Encode(key + string);
int hexLen = hex.length();
int subHexLen = hexLen/8;
String[] ShortStr = new String[4];
for(int i = 0;i < subHexLen;i++){
String outChars = "";
int j = i+1;
String subHex = hex.substring(i*8,j*8);
long idx = Long.valueOf("3FFFFFFF",16) & Long.valueOf(subHex,16);
for(int k = 0;k < 6;k++){
int index = (int)(Long.valueOf("0000003D",16) & idx);//这里取5位没有要求吗？不是取连续的5位
outChars += chars[index];
idx = idx >> 5;
}
ShortStr[i] = outChars;
}
return ShortStr;
}
private final static String[] hexDigits = {
"0","1","2","3","4","5","6","7",
"8","9","a","b","c","d","e","f"
};
public static String byteArrayToHexString(byte[] b){
StringBuffer resultSb = new StringBuffer();
for(int i = 0;i < b.length;i++){
resultSb.append(byteToHexString(b[i]));
}
return resultSb.toString();
}
private static String byteToHexString(byte b){
int n = b;
if(n < 0)
n = 256 + n;
int d1 = n / 16;
int d2 = n % 16;
return hexDigits[d1] + hexDigits[d2];
}
public static String MD5Encode(String origin){
String resultString = null;
try{
resultString = new String(origin);
MessageDigest md = MessageDigest.getInstance("MD5");
resultString.trim();
resultString = byteArrayToHexString(md.digest(resultString.getBytes("UTF-8")));
}catch(Exception ex){}
return resultString;
}
private static void print(Object messagr){
System.out.println(messagr);
}
}
