countScore.java

    public static int countScore(String[] T, String[] R) {
        Map<String, Boolean> groups = new HashMap<>();
        int countOkIndividualTests = 0;
        int countIndividuals = 0;
        final String OK = "OK";
        for (int i = 0; i < T.length; i++) {
            String nameTest = T[i];
            Character lastCharacter = nameTest.charAt(nameTest.length() -1);
            if (lastCharacter >= 'a' && lastCharacter <= 'z') {
                String nameGroup = nameTest.substring(0, nameTest.length() - 1);
                boolean testStatus = R[i].equals(OK);
                boolean testGroupStatus = groups.getOrDefault(nameGroup, true);
                groups.put(nameGroup, testGroupStatus && testStatus);
            }
            else {
                 if (R[i].equals(OK))
                     ++countOkIndividualTests;
                 ++ countIndividuals;
            }

        }
        int countGroupsOK = Collections.frequency(new ArrayList<> (groups.values()) , true);
        double result = ((countGroupsOK + countOkIndividualTests) * 100.0 ) / (countIndividuals + groups.size());
        int resultInt = (int) result;
        int decimalPartAsUnit = (int )((result-resultInt) * 10);
        if (resultInt % 10 < decimalPartAsUnit)
            ++resultInt;
        return resultInt;
    }