Java sha1散列算法的原理解析

public class HashKit {
  private static final char[] HEX_DIGITS = "0123456789abcdef".toCharArray();
  
  public static String sha1(String srcStr){
    return hash("SHA-1", srcStr);
  }
  
  public static String hash(String algorithm, String srcStr) {
      try {
        MessageDigest md = MessageDigest.getInstance(algorithm);
        byte[] bytes = md.digest(srcStr.getBytes("utf-8"));
        return toHex(bytes);
      }
      catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
  
  public static String toHex(byte[] bytes) {
      StringBuilder ret = new StringBuilder(bytes.length * 2);
      for (int i=0; i<bytes.length; i++) {
        ret.append(HEX_DIGITS[(bytes[i] >> 4) & 0x0f]);
        ret.append(HEX_DIGITS[bytes[i] & 0x0f]);
      }
      return ret.toString();
    }
}