# Collision between two ArrayList elements

**URL:** <https://discourse.processing.org/t/collision-between-two-arraylist-elements/5932>\
**Category:** Coding Questions\
**Created:** [November 25, 2018, 6:01pm UTC](https://discourse.processing.org/t/collision-between-two-arraylist-elements/5932 "2018-11-25T18:01:10Z")\
**Posts on this page:** 1\
**Showing post:** 11

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**Author:** ![jeremydouglass](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/jeremydouglass/32/20_2.png) [@jeremydouglass](https://discourse.processing.org/u/jeremydouglass)\
**Post date:** [November 26, 2018, 7:27pm UTC](https://discourse.processing.org/t/collision-between-two-arraylist-elements/5932/11 "2018-11-26T19:27:52Z")

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See also a recent related discussion for examples of interface, and other approaches:

> [@Looping different class instances](https://discourse.processing.org/t/looping-different-class-instances/5843/8):
>
> Abstract classes and reflection are fine solutions given your constraint (no interface!) but I’m a bit confused about why this is an issue. If you don’t want to map a large method list up from Helper to A / B / C, then don’t. You can still use an interface. Just create an interface Helpful with only one method – Helper getHelper(), which returns the Helper object of that A/B/C object. Your classes A B C each implement that one method which makes them Helpful (class A implements Helpful … clas…

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