NetworkAPI.kt

interface NetworkAPI {
    fun sendData(data: String)
}

class HTTPAPI : NetworkAPI {
    override fun sendData(data: String) {
        // send data over HTTP
    }
}

class FTPAPI : NetworkAPI {
    override fun sendData(data: String) {
        // send data over FTP
    }
}

abstract class DataSender {
    protected lateinit var api: NetworkAPI

    abstract fun send()

    fun setAPI(api: NetworkAPI) {
        this.api = api
    }
}

class FileSender(private val filePath: String) : DataSender() {
    override fun send() {
        val fileData = File(filePath).readText()
        api.sendData(fileData)
    }
}

class TextSender(private val text: String) : DataSender() {
    override fun send() {
        api.sendData(text)
    }
}

val fileSender = FileSender("path/to/file.txt")
fileSender.setAPI(HTTPAPI())
fileSender.send()

val textSender = TextSender("some text data")
textSender.setAPI(FTPAPI())
textSender.send()