JAVA - Speed up the code

Question

I want to speed up the my code. Quick status information:

There is more than one list (String) like _list1, _list2, _list3.
I try to find a word (String) in these lists.
If I find a word, I will use index of the word on the list.

Here is my code:

private static int foundIndex (String s) 
{
    if (_list1.contains(s)) {
        return _list1.indexOf(s);
    } else if (_list2.contains(s)) {
        return _list2.indexOf(s);
    } else if (_list3.contains(s)) {
        return _list3.indexOf(s);
    } else if (_list4.contains(s)) {
        return _list4.indexOf(s);
    }
...
...
...
...
    } else if (_list100.contains(s)) {
        return _list100.indexOf(s);
    }
    return -1;
}

How can I speed up the my code?

return index when list is not known ... isn't too much useable — Jacek Cz
– Jacek Cz, Commented Aug 8, 2017 at 19:46
I'm voting to close this question as off-topic because I think it belongs to Code Review — blurfus
– blurfus, Commented Aug 8, 2017 at 19:47
Have you heard of arrays? Having 100 fields named _list1, _list2, ..., _list99, and _list100 is really bad code. — Andreas
– Andreas, Commented Aug 8, 2017 at 19:50

bennyl · Accepted Answer · 2017-08-08 19:53:41Z

2

A couple simple optimizations comes to mind:

1.replace the if (contains) then indexOf pattern with if (i = indexOf(s) >= 0) return i

2.add lookup data structure like a Map<String,Integer> and either use it instead of the lists or in addition to them by updating it whenever you add or change a list

answered Aug 8, 2017 at 19:53

bennyl

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davidxxx · Accepted Answer · 2017-08-08 19:51:28Z

1

Add all your lists (String) in a List<String> and iterate on it :

private static int foundIndex (String s) {
   for (String currentList : lists){
       int indexOf = currentList.indexOf(s);
       if (indexOf != -1) {
          return indexOf;
       }
    }
    return -1;
}

edited Aug 8, 2017 at 19:51

answered Aug 8, 2017 at 19:44

davidxxx

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2 Comments

Jacek Cz Over a year ago

return index when list is not known ... isn't too much useable (like in primary solution)

davidxxx Over a year ago

@Jacek Cz Possible. I don't know the need. With a few modification, it may return a custom class ListAndIndex that contains both the index and the List.

Nickname · Accepted Answer · 2017-08-10 08:57:38Z

0

I changed the algorithm of my code to your suggestions. I was use list to much before, now I changed it. I use 2D String array. But code performance was 157% decrease.

New Code :

private static String[][] _lists = new String[200][100];

private static int foundIndex (String s) {
for (int i = 0; i < 200; i++) {
        for (int j = 0; j < 100; j++) {
            if (_lists[i][j].equals(s) == true) {
                return j;
            }
        }
    }
    return -1;
}

That's where the problem starts.

If the code I'm looking for is "_list[180][?]", it's hard to find it.

How can I speed up the my code?

Thank you.

answered Aug 10, 2017 at 8:57

Nickname

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