Easy way to concatenate two byte arrays in kotlin?

Question

What is the easiest way to concatenate two byte arrays in Kotlin?

Consider,

val x = ByteArray(a);
val y = ByteArray(b);

Help me to concatenate two byte arrays x,y and store it in another ByteArray?

Answer 1

There is a operator function plus for ByteArray (and all other arrays)

operator fun ByteArray.plus(elements: ByteArray): ByteArray

Returns an array containing all elements of the original array and then all elements of the given elements array.

so, you can simply use this function as an operator:

val z ByteArray = x + y

there are also overloaded editions:

operator fun ByteArray.plus(element: Byte): ByteArray


operator fun ByteArray.plus(elements: Collection<Byte>): ByteArray

Please refer this document for details: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/plus.html

BTW, there are many many overloaded editions of this function,

e.g, you can plus a (Iterable<T>, Collection<T>, or Array<T>) and another (Iterable<T>, Collection<T>, Array<T>, or Sequence<T>), then get a List<T>,

or you can plus a Set<T> and another (Array<out T>, Iterable<T>, or Sequence<T>), then get a Set<T>

all these overloaded edition are operator functions, which means you can use it like listA + arrayB

the a + b operator will invoke operator function a.plus(b)

Please refer this document for details: https://kotlinlang.org/docs/reference/operator-overloading.html

Answer 2

fun main(args: Array<String>) {
    val x = ByteArray(a);
    val y = ByteArray(b);

    val xLen = x.size
    val yLen = y.size
    val result = ByteArray(xLen + yLen)

    System.arraycopy(x, 0, result, 0, xLen)
    System.arraycopy(y, 0, result, xLen, yLen)

    // so now result is array that concatenate two byte arrays x,y
}

hope this helps