How to override HashMaps entrySet method in Kotlin? - kotlin

Question

I want to convert java class from this post Retrofit — Multiple query parameters of same name where name is set dynamically to kotlin.
public class ProxyRetrofitQueryMap extends HashMap<String, Object> {
public ProxyRetrofitQueryMap(Map<String, Object> m) {
super(m);
}
#Override
public Set<Entry<String, Object>> entrySet() {
Set<Entry<String, Object>> newSet = new HashSet<>();
return newSet;
}
}
Conversion does not help, it gives Platform declaration clash. I want to manually create Kotlin class which extends from HashMap, but this class does not have entrySet() function. What to do?

Answer 1

When using a kotlin.collections.HashMap or java.util.HashMap, the entrySet() function is accessible through their entries property, which you can override like so:
class ProxyRetrofitQueryMap : HashMap<String, Any>() {
override val entries: MutableSet<MutableMap.MutableEntry<String, Any>>
get() {
val newSet = HashSet<MutableMap.MutableEntry<String, Any>>()
return newSet
}
}
You can confirm that this property maps to the original function by using it in code and then navigating to its declaration in the IDE. Unfortunately, the documentation doesn't seem to state this behaviour explicitly, or at least I couldn't find it.

Answer 2

Here's the full solution, converted to Kotlin:
class ProxyRetrofitQueryMap(m: MutableMap<String, Any>) : HashMap<String, Any>(m) {
override val entries: MutableSet<MutableMap.MutableEntry<String, Any>>
get() {
val originSet: Set<Map.Entry<String?, Any?>> = super.entries
val newSet: MutableSet<MutableMap.MutableEntry<String, Any>> = HashSet()
for ((key, entryValue) in originSet) {
val entryKey = key ?: throw IllegalArgumentException("Query map contained null key.")
// Skip null values
requireNotNull(entryValue) { "Query map contained null value for key '$entryKey'." }
if (entryValue is List<*>) {
for (arrayValue in entryValue) {
if (arrayValue != null) { // Skip null values
val newEntry: MutableMap.MutableEntry<String, Any> =
SimpleEntry(entryKey, arrayValue)
newSet.add(newEntry)
}
}
} else {
val newEntry: MutableMap.MutableEntry<String, Any> = SimpleEntry(entryKey, entryValue)
newSet.add(newEntry)
}
}
return newSet
}
}