Custom Containers

Custom containers are a way to provide your own implementation of standard container types, enabling extensibility of the collections language.

Example: weakHashMap

Provided the following declaration is reachable from the model currently being edited...

custom containers WeakCollections {                       
                                                          
  public container weakHashMap<K, V> specifies map<K, V> {
    runtime type: WeakHashMap<K, V>                       
    factory: <no factory>                                 
  }                                                       
                                                          
  public container weakHashSet<E> specifies set<E> {      
    runtime type: WeakSet<E>                              
    factory: <no factory>                                 
  }                                                       
                                                          
}

... you can use the weak version of hashmap like this:

map<Object, int> myMap= new weakHashMap<Object, int>;

Custom Containers Declaration

A root node of concept CustomContainers may have one or more declarations.

[public|protected|private] container containerName<TypeVar, ...> specifies container_type<TypeVar, ...> {
  runtime type: Classifier<TypeVar, ...>
  factory: expression of type Classifier<> (optional)
}

declaration part	allowed contents
containerName	any valid identifier
container_type	one of the existing container types of the collections language
runtime type	Java classifier that represents the implementation of the container
factory	(optional) container creation expression; the classifier's default constructor used if undefined

06 May 2026