How to update existing MongoDB Collection Validation?

Question

I have created a MongoDB Collection using the following code, I want to update this collection add a new column named "username" and also want to change the data type of roleId from String to Long. Please advice how to do this in Java Mongo API

fun createUsers(mongoDB: MongoDatabase) {

    var collOptions: ValidationOptions = ValidationOptions()

    collOptions.validator(
            Filters.and(
                    Filters.exists("userId"),
                    Filters.type("userId",BsonType.STRING),
                    Filters.exists("roleId"),
                    Filters.type("roleId", BsonType.INT32)
            )
    )

    collOptions.validationLevel(ValidationLevel.STRICT)
    collOptions.validationAction(ValidationAction.ERROR)

    mongoDB.createCollection("user", CreateCollectionOptions().validationOptions(collOptions))
}