codewars #39 Help the bookseller ! (6kyu)

#39 Help the bookseller ! 

A bookseller has lots of books classified in 26 categories labeled A, B, ... Z. Each book has a code of 3, 4, 5 or more capitals letters. The first letter of a letter is the capital letter of the book category. In the bookseller's stocklist each code is followed by a space and a positive integer n (int n> = 0) which indicates the quantity of books in this code in stock.

For example an extract of one of the stocklists could be:

L = {"ABART 20", "CDXEF 50", "BKWRK 25", "BTSQZ 89", "DRTYM 60"}.

or

L = ["ABART 20", "CDXEF 50", "BKWRK 25", "BTSQZ 89", "DRTYM 60"] or ....

You will be given a stocklist (L) and a list of categories in capital letters.

  M = {"A", "B", "C", "W"}

or

  M = ["A", "B", "C", "W"] or ...

and your task is to find all the books of L with codes belonging to each category.

For the lists L and M, you have to return the string (in Haskell / Clojure a list of pairs):

  (A: 20) - (B: 114) - (C: 50) - (W: 0)

"BKWRK" and "BTSQZ", 50 corresponding to "CDXEF" and 0 to category 'W', where A, B, C and W are the categories, since there is no code beginning with W.

If L or M are empty return string is "" (Clojure should return an empty array instead).

import java.util.ArrayList;
import java.util.List;

public class StockList { 
	
	// 1st parameter is the stocklist (L in example), 
	// 2nd parameter is list of categories (M in example)
	public static String stockSummary(String[] lstOfArt, String[] lstOf1stLetter) {
		// your code here
		if(lstOfArt.length== 0 || lstOf1stLetter.length == 0) return "";
		List<String> result = new ArrayList<String>();
		for (String letter : lstOf1stLetter) {
			int temp = 0;
			for (String art : lstOfArt) {
				if(art.startsWith(letter)) temp += Integer.valueOf(art.split(" ")[1]);
			}
			result.add("("+letter+" : "+temp+")");
		}
		
		return String.join(" - ", result);
	}
}