Implement MD5 encryption of strings or files under Android

MD5-Information Digest Algorithm Brief Introduction

• MD5 (Message-Digest Algorithm), a widely used cryptographic hash function, can generate a 128-bit (16-byte) hash value (hash value) to ensure the integrity and consistency of information transmission.
• The calculated MD5 value may be repeated, but the probability is very low.
• The encryption process is almost irreversible, unless a huge Key-Value database is maintained for collision cracking, it is almost impossible to unlock
• The string encrypted by MD5 is fixed, and the result of each encryption of the same string or file remains unchanged

Code implementation under Android

• The following code implements the general 32-bit md5 calculation, and the calculation results keep the generated characters as hexadecimal strings with a length of 32, which can be directly translated and used when needed in development

  public class Md5Util {
      public static String get(String text) {
          String result = null;
          try {
              MessageDigest md = MessageDigest.getInstance("MD5");
              byte[] digest = md.digest(text.getBytes());
              result = toHexString(digest);
          } catch (NoSuchAlgorithmException ex) {
              ex.printStackTrace();
          }
          return result;
      }
  
      public static String get(InputStream inputStream) {
          String result = null;
          try {
              byte[] buffer = new byte[8192];
              int len;
              MessageDigest md = MessageDigest.getInstance("MD5");
              while ((len = inputStream.read(buffer)) != -1) {//分多次读入文件，占用内存比较少
                  md.update(buffer, 0, len);
              }
              inputStream.close();
  
              byte[] digest = md.digest();
              result = toHexString(digest);
          } catch (Exception ex) {
              ex.printStackTrace();
              if (inputStream != null) {
                  try {
                      inputStream.close();
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              }
          }
          return result;
      }
  
      public static String get(File file) {
          String result = null;
          try {
              result = get(new FileInputStream(file));
          } catch (FileNotFoundException e) {
              e.printStackTrace();
          }
          return result;
      }
  
      private static String toHexString(byte[] digest) {
          StringBuilder sb = new StringBuilder();
          String hexStr;
          for (byte b : digest) {
              hexStr = Integer.toHexString(b & 0xFF);//& 0xFF处理负数
              if (hexStr.length() == 1) {//长度等于1，前面进行补0，保证最后的字符串长度为32
                  hexStr = "0" + hexStr;
              }
              sb.append(hexStr);
          }
  
          return sb.toString();
      }
  }