CollectionJsonAdapter.kt

package de.everhome.sdk.json

abstract class CollectionJsonAdapter<C : MutableCollection<T>, T>(private val elementAdapter: JsonAdapter<T>) : JsonAdapter<C>() {

    override fun fromJson(reader: JsonReader): C? {
        if (reader.peek() != Token.BEGIN_ARRAY) {
            reader.skipValue()
            return null
        }
        val result = newCollection()
        reader.beginArray()
        while (reader.hasNext()) {
            val value = elementAdapter.fromJson(reader)
            if (value != null) {
                result.add(value)
            }
        }
        reader.endArray()
        return result
    }

    override fun toJson(writer: JsonWriter, value: C?) {
        if (value == null) return
        writer.beginArray()
        for (element in value) {
            elementAdapter.toJson(writer, element)
        }
        writer.endArray()
    }

    abstract fun newCollection(): C
}

ListJsonAdapter.kt

package de.everhome.sdk.json

class ListJsonAdapter<T>(elementAdapter: JsonAdapter<T>) : CollectionJsonAdapter<MutableList<T>, T>(elementAdapter) {
    override fun newCollection(): MutableList<T> {
        return mutableListOf()
    }
}