Generating Methods of MD5 in Android Summary of of

Java provides MessageDigest classes for processing message digest algorithms, such as MD5, SHA-1, and SHA-256.

1. Standard implementation of Java

Use bit operation for binary conversion.

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

public class Hash {

  private static final char[] hexCode = "0123456789ABCDEF".toCharArray();

  public static String md5(String input) throws NoSuchAlgorithmException {
    byte[] bytes = MessageDigest.getInstance("MD5").digest(input.getBytes());
    return printHexBinary(bytes);
  }

  public static String printHexBinary(byte[] data) {
    StringBuilder r = new StringBuilder(data.length * 2);
    for (byte b : data) {
      r.append(hexCode[(b >> 4) & 0xF]);
      r.append(hexCode[(b & 0xF)]);
    }
    return r.toString();
  }
}

2. Use String. format

Use String. format for binary conversion.

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

public class Hash {

  public static String md5(String input) throws NoSuchAlgorithmException {
    byte[] bytes = MessageDigest.getInstance("MD5").digest(input.getBytes());
    return printHexBinary(bytes);
  }

  public static String printHexBinary(byte[] data) {
    StringBuilder r = new StringBuilder(data.length * 2);
    for (byte b : data) {
      r.append(String.format("%02X", new Integer(b & 0xFF)));
    }
    return r.toString();
  }
}

3. Standard Implementation of Kotlin

object Hash {

  private val HEX_CHARS = "0123456789ABCDEF".toCharArray()

  fun md5(input: String): String {
    val bytes = MessageDigest.getInstance("MD5").digest(input.toByteArray())
    return printHexBinary(bytes)
  }

  fun printHexBinary(data: ByteArray): String {
    val r = StringBuilder(data.size * 2)
    data.forEach { b ->
      val i = b.toInt()
      r.append(HEX_CHARS[i shr 4 and 0xF])
      r.append(HEX_CHARS[i and 0xF])
    }
    return r.toString()
  }
}

4. Kotlin extension function

fun String.md5(): String {
  val bytes = MessageDigest.getInstance("MD5").digest(this.toByteArray())
  return bytes.hex()
}

fun ByteArray.hex(): String {
  return joinToString("") { "%02X".format(it) }
}

After defining the extension function, you can use the following syntax to calculate the MD5 value:

val hash = "foo-bar".md5()