Convert a Map to a List, Array or Set in Java
Convert a map to a list, array or set in Java using keySet(), values() and entrySet(), with streams, toArray(), ordering rules and lists of records.
Convert List to Map in Java: toMap(), Duplicate Keys and Order
Convert List to Map in Java with Collectors.toMap() and groupingBy(), fix the duplicate key IllegalStateException with a merge function, keep order.