How to convert Java into Kotlin

Question

I don't know if somebody has already answered this question. If it's the case, then, please for the redondancy.

I would like to transform this function into Kotlin function. Thanks for the help.

private final static String HEX = "XXXXXXXXX";
private static void appendHex(StringBuffer sb, byte b) {
    sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
}

Answer 1

I suggest using an extension function for that:

private const val HEX = "XXXXXXXXX"
fun StringBuffer.appendHex(b: Byte): StringBuffer {
    val i = b.toInt()
    append(HEX[i shr 4 and 0x0f])
    append(HEX[i and 0x0f])
    return this
}

I also made the function return this again so you can even call it in a chain:

myStringBuffer
   .append(someThing)
   .appendHex(myByte)
   .append(someThingElse)

Answer 2

If it's just a hex string representation you need (and that's also what I get from your comment), you may just want to use the following instead:

fun StringBuffer.appendHex(b : Byte) = append("%02X".format(b))

Usage is then the same as also Lino has shown:

StringBuffer()
    .append("some text")
    .appendHex(someByte)

or if you need to keep your current signature:

companion object {
  @JvmStatic
  fun appendHex(s : StringBuffer, b : Byte) {
    s.append("%02X".format(b))
  }
}

Answer 3

companion object {
    private const val HEX = "XXXXXXXXX"

    @JvmStatic
    private fun appendHex(sb: StringBuffer, b: Int) {
        sb.append(HEX[b shr 4 and 0x0f]).append(HEX[b and 0x0f])
    }
}

Please note that I had to change the Byte to Int , because Byte doesn't seem to have shr and and defined for some unknown reason.

No, I really don't know why bitwise operators would not be defined over byte .