Java implementation of MD5 encryption method summary

A code:

public class MD5 {
   
  
  public static String stringMD5(String pw) {
    try { 
        
       //Get an MD5 converter (if you want SHA1 instead of "SHA1")
       MessageDigest messageDigest =MessageDigest.getInstance("MD5"); 
       //The input string is converted into a byte array
       byte[] inputByteArray = pw.getBytes(); 
       //InputByteArray is an array of bytes converted from an input string
       messageDigest.update(inputByteArray); 
       //Converts and returns the result, also a byte array, containing 16 elements
       byte[] resultByteArray = messageDigest.digest(); 
       //Returns an array of characters converted to a string
       return byteArrayToHex(resultByteArray); 
      } catch (NoSuchAlgorithmException e) { 
       return null; 
      } 
  }
   
  public static String byteArrayToHex(byte[] byteArray) { 
     
    //First, an array of characters is initialized to hold each hexadecimal character
    char[] hexDigits = {'0','1','2','3','4','5','6','7','8','9', 'A','B','C','D','E','F' }; 
    //A byte is a binary of eight bits, or two hexadecimal characters (2 to the eighth is equal to 16 to the second).
    char[] resultCharArray =new char[byteArray.length * 2]; 
    //Traversing the byte array, by bit operation (bit operation is efficient), converts the character into the character array to go
    int index = 0; 
    for (byte b : byteArray) { 
      resultCharArray[index++] = hexDigits[b>>> 4 & 0xf]; 
      resultCharArray[index++] = hexDigits[b& 0xf]; 
    }
    //The array of characters is returned as a string
    return new String(resultCharArray); 
  }
}

Method 2:

package other;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5 {
  
  //Global array
  private final static String[] strDigits = { "0", "1", "2", "3", "4", "5",
      "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };

  public MD5() {
  }

  //Returns a number and a string
  private static String byteToArrayString(byte bByte) {
    int iRet = bByte;
    // System.out.println("iRet="+iRet);
    if (iRet < 0) {
      iRet += 256;
    }
    int iD1 = iRet / 16;
    int iD2 = iRet % 16;
    return strDigits[iD1] + strDigits[iD2];
  }

  //Return form only for Numbers
  private static String byteToNum(byte bByte) {
    int iRet = bByte;
    System.out.println("iRet1=" + iRet);
    if (iRet < 0) {
      iRet += 256;
    }
    return String.valueOf(iRet);
  }

  //Converts the byte array to a hexadecimal string
  private static String byteToString(byte[] bByte) {
    StringBuffer sBuffer = new StringBuffer();
    for (int i = 0; i < bByte.length; i++) {
      sBuffer.append(byteToArrayString(bByte[i]));
    }
    return sBuffer.toString();
  }

  public static String GetMD5Code(String strObj) {
    String resultString = null;
    try {
      resultString = new String(strObj);
      MessageDigest md = MessageDigest.getInstance("MD5");
      //The function md.digest() returns a byte array of hash results
      resultString = byteToString(md.digest(strObj.getBytes()));
    } catch (NoSuchAlgorithmException ex) {
      ex.printStackTrace();
    }
    return resultString;
  }

  public static void main(String[] args) {
    MD5 getMD5 = new MD5();
    System.out.println(getMD5.GetMD5Code("000000"));
  }
}