java - Categorize ArrayList of objects based on their property -

i have arraylist of products, , each product has category property (so each category can have many products). need format data products categorized according category property.

i think hashmap useful, use category key , arraylist of products value.

if correct approach, can assist me logic involved in turning arraylist hashmap have described? or maybe there better way of handling it.

/** update **/

here sample method, i'm not sure how make logic happen:

private hashmap<string, arraylist> sortproductsbycategory (arraylist<product> productlist) {      // hashmap value category name, , value array of products     hashmap<string, arraylist> map;      for(product product: productlist) {          // if key not exist in hashmap         if(!map.containskey(product.getcategory()) {             // add key map, add product new arraylist         }         else {             // add product arraylist corresponds key         }         return map;      }   } 

yes, absolutely valid approach want switch "1-dimensional" view "2-dimensional".