Krdytkyu

This calculates the number of occurrences of each symbol in a string array.

I want to find some places in this multithreading code which could lead to a NullPointerException or other exceptions or vulnerabilities.

public class StringCount extends RecursiveTask<Map<Character, Integer>> {

    private int UNIT_SIZE = 1;

    private String values;

    private int startPos, endPos;



    public StringCount(String values) {

        this(values, 0, values.length);

    }



    public StringCount(String values, int startPos, int endPos) {

        this.values = values;

        this.startPos = startPos;

        this.endPos = endPos;

    }



    protected Map<Character, Integer> compute() {

        final int currentSize = endPos - startPos;

        if (currentSize <= UNIT_SIZE) {

            return computeSum();

        }

        else {

            int center = currentSize / 2;

            int leftEnd = startPos + center;

            StringCount leftSum = new StringCount(values, startPos, leftEnd);

            leftSum.fork();

            int rightStart = startPos + center;

            StringCount rightSum = new StringCount(values, rightStart, endPos);

            Map<Character, Integer> map = rightSum.compute();

            Map<Character, Integer> map1 = leftSum.join();

            for (Character character : map1.keySet()) {

                if (!map.containsKey(character))

                    map.put(character, 0);

                map.put(character, map1.get(character) + map.get(character));

            }

            return map;

        }

    }



    private Map<Character, Integer> computeSum() {

        Map<Character, Integer> map = new HashMap<>();

        for (int i = startPos; i < endPos; i++) {

            if (values[i] == null) break;

            for (int j = 0; j < values[i].length(); j++) {

                Character c = values[i].toLowerCase().charAt(j);

                if (!map.containsKey(c)) map.put(c, 0);

                map.put(c, map.get(c) + 1);

            }

        }

        if (map.size() == 0)map.put(' ', 0);

        return map;

    }



    public static void main(String args) {

        String stringArray = new String[100];

        for (int i = 0; i < stringArray.length; i++) {

            stringArray[i] = "ldlihnvlCdnfcs;dgnhreieue tr;srdrgy    rfguhy.";

        }

        ForkJoinPool pool = new ForkJoinPool();

        StringCount calculator = new StringCount(stringArray);

        System.out.println(pool.invoke(calculator));

    }

}