Several ways to generate MD5 in Android (summary)

Java provides the MessageDigest class to handle message digest algorithms, such as MD5, SHA-1 and SHA-256.

1. Java standard implementation

Use bit operations for the binary conversion.

import ;
import ;

public class Hash {

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

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

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

2. Use

Use for binary conversion.

import ;
import ;

public class Hash {

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

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

3. Kotlin's standard implementation

object Hash {

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

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

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

4. Kotlin extension function

fun String.md5(): String {
  val bytes = ("MD5").digest(())
  return ()
}

fun (): 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()

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