java performance : Is storing a hashMap value in a variable redundant?

Question

my goal is to reduce memory usage. should I store a hashMap value in a variable if I need to use that value multiple times?

public void upcCheck() {
          String prodUPC = pHashMap.get("productUpc");
          if(prodUpc == ''){
            //do stuff;
          }
          else if(prodUpc == '0123456'){
            //do other stuff;
          }
    }

Or should I just always use the hashMap's get() method to avoid redundancy and unecessary memory usage?

 public void upcCheck() {

              if(pHashMap.get("productUpc") == ''){
                //do stuff;
              }
              else if(pHashMap.get("productUpc") == '0123456'){
                //do other stuff;
              }
        }

The hashMap contains alot of values ae: product type, product price etc... Many methods are set to work with those values. So I was wondering about the best approach. Thank you!

Answer 1

It's not redundant, and doesn't take a lot of extra memory. Extra variables don't take much memory; as this post mentions, there is no standard amount (it depends on the vm), but the amount is small enough to not worry about.

In a situation like this, if you were using a List, it would matter, seeing how accessing that list can increase in time depending on the size of the array. This measurement of time is called the time complexity. Although, since you're using a Map, it's not something to worry about.

I would prefer using the extra variable, since it's personally easier to read. It's always best to prefer readability. Removing the variable will not cause any noticable performance boosts, seeing how it doesn't take much memory at all, and shouldn't be something to worry about.