SHA1加密算法

public static String getSha1(String str){
if(str == null || str.length() == 0){
return null;
}
char hexDigits[] = {'0','1','2','3','4','5','6','7','8','9',
'a','b','c','d','e','f'};
try{
MessageDigest mdTemp = MessageDigest.getInstance("SHA1");
mdTemp.update(str.getBytes("UTF-8"));

byte[] md = mdTemp.digest();
int j = md.length;
char buf[] = new char[j*2];
int k = 0;
for(int i = 0; i<j; i++){
byte byte0 = md[i];
buf[k++] = hexDigits[byte0 >>> 4 & 0xf];
buf[k++] = hexDigits[byte0 & 0xf];
}
return new String(buf);
}catch(Exception e){
return null;
}
}