Java Quiz class

so i have this problem that is asking me to finish a test class and fill in the blanks basically and ive drawn a few blanks just asking for some help

(10 points on a test)

Test class

Variables

        private ArrayList<Problem> probList;

Constructors

        //probList should be empty

        public Test()



        //probList should be populated by

public Test(Problem[] probs)

Methods

        //add problem to the end of test

        public void addProblem(Problem prob)



        /*

Should return a string containing each question, numbered and separated by a line.

Example:

What is 5+5?

Who won the Civil War?

A. The North

B. The South

C. Your Mom

*/

        public String toString()



        //Returns the percent of answers answered correctly.

        //Precondition: answers.length == probList.size()

        //Values of answers may be null

        public int gradeTest(String[] answers)



        /*

Returns a numbered list of answers:

10 A

*/

        public String answerKey()