Classes FRQ

public class Cat {
    // instance variable sound
    private String sound;

    /**
     * constructor with noise input for sound
     *
     * @param noise sound
     */
    public Cat(String noise) {
        sound = noise;
    }

    /**
     * returns sound in all lowercase
     *
     * @return lowercase sound
     */
    public String makeQuietNoise() {
        return sound.toLowerCase(); // using toLowerCase() to convert String to lowercase
    }

    /**
     * returns sound in reverse
     *
     * @return reverse sound
     */
    public String makeReverseNoise() {
        return new StringBuilder(sound).reverse().toString(); // using StringBuilder class to reverse the String, then covert it back to String with toString()
    }
}

public interface StudyPractice {
    /**
     * returns the current practice problem
     */
    String getProblem();

    /**
     * changes to the next practice problem
     */
    void nextProblem();
}

public class MultPractice implements StudyPractice {
    // instance variables for the two integers c1 and c2
    private int c1, c2;

    /**
     * constructor that initializes c1 and c2
     *
     * @param c1 first integer
     * @param c2 second integer
     */
    public MultPractice(int c1, int c2) {
        this.c1 = c1;
        this.c2 = c2;
    }

    /**
     * prints out the problem, similar to a toString function
     *
     * @return c1 TIMES c2
     */
    public String getProblem() {
        return c1 + " TIMES " + c2; // String concatenation
    }

    /**
     * updates to the next problem
     */
    public void nextProblem() {
        c2++; // adds one to c2 to produce next problem
    }
}