Custom-Checker body section for list of 5 prime numbers under 100

CustomCheckerBody.java

// Start of BODY
public class CustomChecker {

    static boolean is_prime_number(int n) {
        for(int i=2;i<n;i++) {
            if(n%i==0)
                return false;
        }

        return true;
    }

    static void run_custom_checker(final TestStruct t_obj, ResultStruct r_obj) {
        // Read contents of the result file
        String result_data;
        try {
            BufferedReader br = new BufferedReader(new FileReader(t_obj.testcase_output_path));
            StringBuilder sb = new StringBuilder();
            String line = br.readLine();

            while (line != null) {
                sb.append(line);
                sb.append(System.lineSeparator());
                line = br.readLine();
            }
            br.close();

            result_data = sb.toString();
        } catch(IOException e) {
            r_obj.result = false;
            r_obj.score = 0;
            r_obj.message = "Error reading result file";
            return;
        } 

        String []values = result_data.split(" |\n");

        // Make sure all the values are unique
        Set<String> uniq_values = new HashSet<String>(Arrays.asList(values));

        // Count the number of primes
        int correct_values = 0;
        for(String value:uniq_values) {
            if (!value.isEmpty() && is_prime_number( Integer.parseInt(value) ) )
                correct_values++;
        }
        
        // Cutoff score to determine success
        if(correct_values > 3)
            r_obj.result = true;
        else
            r_obj.result = false;

        r_obj.score = (float)correct_values / 5;
        r_obj.message = correct_values + " out of 5 values are correct";
    }

// End of BODY