Android编程之MD5加密算法实例分析

package com.tencent.utils;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/** 
 * 对外提供getMD5(String)方法 
 * @author randyjia 
 * 
 */ 
public class MD5 {
 public static String getMD5(String val) throws NoSuchAlgorithmException{
  MessageDigest md5 = MessageDigest.getInstance("MD5");
  md5.update(val.getBytes());
  byte[] m = md5.digest();//加密
  return getString(m);
}
 private static String getString(byte[] b){
  StringBuffer sb = new StringBuffer();
   for(int i = 0; i < b.length; i ++){
   sb.append(b[i]);
   }
   return sb.toString();
}
}

/* 
* MD5加密 
*/ 
private String getMD5Str(String str) {
  MessageDigest messageDigest = null;
  try {
   messageDigest = MessageDigest.getInstance("MD5");
   messageDigest.reset();
   messageDigest.update(str.getBytes("UTF-8"));
  } catch (NoSuchAlgorithmException e) {
   System.out.println("NoSuchAlgorithmException caught!");
   System.exit(-1);
  } catch (UnsupportedEncodingException e) {
   e.printStackTrace();
  }
  byte[] byteArray = messageDigest.digest();
  StringBuffer md5StrBuff = new StringBuffer();
  for (int i = 0; i < byteArray.length; i++) {
   if (Integer.toHexString(0xFF & byteArray[i]).length() == 1)
    md5StrBuff.append("0").append(Integer.toHexString(0xFF & byteArray[i]));
   else
    md5StrBuff.append(Integer.toHexString(0xFF & byteArray[i]));
  }
 //16位加密，从第9位到25位
  return md5StrBuff.substring(8, 24).toString().toUpperCase();
}

public static String md5(String string) {
 byte[] hash;
 try {
  hash = MessageDigest.getInstance("MD5").digest(string.getBytes("UTF-8"));
 } catch (NoSuchAlgorithmException e) {
  throw new RuntimeException("Huh, MD5 should be supported?", e);
 } catch (UnsupportedEncodingException e) {
  throw new RuntimeException("Huh, UTF-8 should be supported?", e);
 }
 StringBuilder hex = new StringBuilder(hash.length * 2);
 for (byte b : hash) {
  if ((b & 0xFF) < 0x10) hex.append("0");
  hex.append(Integer.toHexString(b & 0xFF));
 }
 return hex.toString();
}