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

/**
 * Collects problems that are encountered during settings building.
 *
 */
class DefaultProblemCollector implements ProblemCollector {

    private final List<Problem> problems;

    private String source;

    DefaultProblemCollector(List<Problem> problems) {
        this.problems = (problems != null) ? problems : new ArrayList<>();
    }

    @Override

import static org.junit.jupiter.api.Assertions.assertNull;

class DefaultProblemCollectorTest {

    @Test
    void testGetProblems() {
        DefaultProblemCollector collector = new DefaultProblemCollector(null);
        assertNotNull(collector.getProblems());
        assertEquals(0, collector.getProblems().size());

        collector.add(null, "MESSAGE1", -1, -1, null);

     * @param problems starting set of problems, may be {@code null}
     * @return a new instance of a ProblemCollector
     */
    public static ProblemCollector newInstance(List<Problem> problems) {
        return new DefaultProblemCollector(problems);
    }