HashMap errors - containsKey, get

Question

Can anyone shed some light?

Problem code:

protected var table = HashMap<Class<*>, Double>()

if (table.containsKey(object)) {
    value = table.get(object)
} 

containsKey(K):Boolean is deprecated. Map and Key have incompatible types. upcast to Any? if you're sure

so I changed it to this:

if (table.containsKey(object as Any?)

which fixes the error, but is this what I should have done to fix it? or is there a better way?

also .get(object) has an error:

Type inference failed. required: kotlin.Double found kotlin.Double?

same error message for this too:

val c = someObject.javaClass // pre j2k code: final Class<? extends SomeClass> c = someObject.getClass();
weight = weightingTable[c] <-- error here

I don't know what to do here

Answer 1

The containsKey call is reported as an error because the type of the argument you pass to it does not match the type of the map key. Your map contains classes as keys, and you're trying to pass an object instance to it. Changing this to object as Any? is not a useful fix, because this call will compile but will always return false. What you need to do instead is to use object.javaClass to get the class of the object.

The weightingTable[c] call is reported as an error because the map does not necessarily contain a value for the key you're passing to it, so the result of the [] operation is nullable. You cannot assign a nullable value to a non-null variable without somehow handling the null case (using a check, an explicit non-null cast or some other option covered in the documentation).

Answer 2

When doing:

myHashMap.get(object)

and getting:

Type inference failed. required: kotlin.Double found kotlin.Double?

even when you already checked with containsKey. You can solve it by using:

myHashMap.getOrElse(key) { defaultValue }