Create zip in memory.

Main.kt

import java.io.*
import java.util.zip.ZipEntry
import java.util.zip.ZipOutputStream


fun main() {
    val sourcePath = "toZip"
    val outputStream = ByteArrayOutputStream()

    try {
        createZipInMemory(sourcePath, outputStream)
        // You can now use the outputStream to access the zipped data
    } catch (e: IOException) {
        e.printStackTrace()
    }

    File("test-zip.zip").writeBytes(outputStream.toByteArray())
}

fun createZipInMemory(sourcePath: String, outputStream: ByteArrayOutputStream) {
    ZipOutputStream(BufferedOutputStream(outputStream)).use { zipOut ->
        val sourceFile = File(sourcePath)
        compressFile(sourceFile, sourceFile.name, zipOut)
    }
}

fun compressFile(fileToZip: File, fileName: String, zipOut: ZipOutputStream) {
    if (fileToZip.isHidden) {
        return
    }
    if (fileToZip.isDirectory) {
        val entries = fileToZip.listFiles() ?: return
        if (fileName.endsWith("/")) {
            zipOut.putNextEntry(ZipEntry(fileName))
            zipOut.closeEntry()
        } else {
            zipOut.putNextEntry(ZipEntry("$fileName/"))
            zipOut.closeEntry()
        }
        for (childFile in entries) {
            compressFile(childFile, "$fileName/${childFile.name}", zipOut)
        }
        return
    }

    fileToZip.inputStream().use { fis ->
        val zipEntry = ZipEntry(fileName)
        zipOut.putNextEntry(zipEntry)
        val bytes = ByteArray(1024)
        var length: Int
        while (fis.read(bytes).also { length = it } >= 0) {
            zipOut.write(bytes, 0, length)
        }
        zipOut.closeEntry()
    }
}