> For the complete documentation index, see [llms.txt](https://hanfak.gitbook.io/workspace/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hanfak.gitbook.io/workspace/general-paradigms/patterns/api/weakest-type.md).

# Weakest type

* For inputs
  * Instead of conreate impl, use interfaces
  * instead of ArrayList, use List, or Collection (if dont care about ordering) or ITerable (if dont care about the size)
    * This gives the user more flexibility, can use method with ArrayList, LinkedList etc
    * Reduces need to add more convience methods for different methods
    * avoids overloading
* For return type
  * Does it matter the need for the concreteness of impl or sub class with extra properties/behaviour
* Make the type more abstract, allows for change in implementatoin of api, without breaking the user
  * more flexibility
* As the signature is a contract with the user.
  * if the contract says the return type is a collection, and the user is uses this as so, then they are breaking the contract, not the developer