Challenges

Remember the rules for this are

Try to use only the information given up to this point in this book.
Try not to give up until you've given it a solid attempt

Challenge 1.

The following classes are named "wrong." Name them correctly.

class gonzo {}

class fozzie_the_bear {}

class MSPIGGY {}

void main() {
    IO.println(new gonzo());
    IO.println(new fozzie_the_bear());
    IO.println(new MSPIGGY());
}

Challenge 2.

Make a variable named movie which is an instance of the Movie class. Set the value of its title field to Muppets in Space.

class Movie {
    String title;
}

void main() {
    // ---------------
    // CODE HERE
    // ---------------

    IO.println(
        movie.title
    );
}

Challenge 3.

Alter the ThemePark class so that the default value for its entranceFee field is 35.24.

class ThemePark {
    double entranceFee;
}

void main() {
    ThemePark themePark = new ThemePark();

    IO.println(
        themePark.entranceFee
    );
}

Challenge 4.

Changing only the indicated line, make it so the word Kermit only appears twice in the program.

Hint: Remember that inferred types exist.

class Kermit {
    boolean angry = true;
}

void main() {
    // ------------------------
    // CHANGE ONLY THIS LINE v
    Kermit kermit = new Kermit();
    // ------------------------

    IO.println(kermit.angry);
}

Challenge 5.

Make a method named squareRoot which returns an instance of the SquareRoot class containing both the positiveRoot and negativeRoot of the given double.

So if you are given 4 you should return a positive root of 2 and a negative root of -2.

You do not have to account for the possibility of being given a negative number. You should use Math.sqrt to find the positive root and common sense to find the negative root.

class SquareRoot {
    double positiveRoot;
    double negativeRoot;
}

SquareRoot squareRoot(double value) {
    // -----------
    // CODE HERE
    // -----------
}

void main() {
    SquareRoot sqrtOfFour = squareRoot(4);
    // 2
    IO.println(sqrtOfFour.positiveRoot);
    // -2
    IO.println(sqrtOfFour.negativeRoot);

    SquareRoot sqrtOfFifteen = squareRoot(15);
    // 3.872983346207417
    IO.println(sqrtOfFifteen.positiveRoot);
    // -3.872983346207417
    IO.println(sqrtOfFifteen.negativeRoot);
}

Challenge 6.

Only writing code between the lines and without directly accessing any fields on or reassigning the actor variable, make the program output Tim Curry.

Hint: The key word is "directly."

class Actor {
    String name;
}

void main() {
    Actor actor = new Actor();
    actor.name = "Frog, Kermit the";

    // --------------------------
    // CODE HERE
    // --------------------------

    IO.println(actor.name);
}

Modern Java