Kotlin program converts byte array to hexadecimal

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In this program, you will learn different methods to convert a byte array to hexadecimal in Kotlin.

Example1：Convert byte array to hexadecimal value

fun main(args: Array<String>) {
　　　　val bytes = byteArrayOf(10,　2,　15,　11)
　　　　for (b in bytes) {
　　　　　　　　val st = String.format("%02X", b)
　　　　　　　　print(st)
　　　　}
}

When running the program, the output is:

0A020F0B

In the above program, we have an array named bytes. To convert the byte array to a hexadecimal value, we iterate over each byte in the array and use String's format().

We use%02X prints two positions (02) hexadecimal (X) value and store it in the string st.

For large byte array conversion, this is a relatively slow process. We can use the byte operations shown below to greatly improve execution speed.

Example2：Convert byte array to hexadecimal value using byte operations

import kotlin.experimental.and
private val hexArray = "0123456789ABCDEF".toCharArray()
fun bytesToHex(bytes: ByteArray): String {
　　　　val hexChars = CharArray(bytes.size　*　2)
　　　　for (j in bytes.indices) {
　　　　　　　　val v = (bytes[j] and 0xFF.toByte()).toInt()
　　　　　　　　hexChars[j　*　2] = hexArray[v ushr}　4]
　　　　　　　　hexChars[j　*　2　+　1] = hexArray[v and 0x0F]
　　　　}
　　　　return String(hexChars)
}
fun main(args: Array<String>) {
　　　　val bytes = byteArrayOf(10,　2,　15,　11)
　　　　val s = bytesToHex(bytes)
　　　　println(s)
}

The output of this program is the same as the example1Same.

This is the equivalent Java code:Java Program to Convert Byte Array to Hexadecimal.

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