title: how to make an array list for each value in another array list in android studio
body: <p>I want to create an app that counts my expenses. I created array list for trips and now I want to create array list for categories and another array list for each category. for example, in trip1 I have 3 categories: a, b, c. and in every category, I have my expenses. so how I make an array list for each value in the trip array list?</p>