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.

Will this code run? Why or why not.

int compute(int x) {
    if (x == 0) {
        return null;
    }
    else {
        return x * x;
    }
}

void main() {
    System.out.println(compute(5));
}

Challenge 2.

Write a method which takes in a Integer[] representing a series of distances and prints out every distance followed by kilometers.

So if the array has 1, 2, and 3 you should output

1 kilometers
2 kilometers
3 kilometers

If this method is given null, it should act as if it was given an empty array.

void printDistances(Integer[] distances) {

}

void main() {
    printNames(new String[] {
        45,
        99,
        23
    });
}

Challenge 3.

Write a method called onlyPositive which takes in an int and returns the same value out if the number is greater than zero.

If the number is less than or equal to zero, return null.

// Write onlyPositive here

void main() {
    // 45
    System.out.println(
        onlyPositive(45)
    );

    // 46
    System.out.println(
        onlyPositive(45) + 1
    );

    // null
    System.out.println(
        onlyPositive(0)
    );

    // null
    System.out.println(
        onlyPositive(-1)
    );
}

Challenge 4.

Will the following code work? Why or why not?

void main() {
    int ducks = 5;
    Integer sparrows = 3;

    int birds = ducks + sparrows;

    System.out.println(birds);
}

Challenge 4.

Will the following code work? Why or why not?

void main() {
    char[] face = new char[] { ':', ')' };
    Character[] smile = face;

    System.out.println(smile);
}

Challenge 5.

Will the following code work? Why or why not?

void main() {
    char[] face = new char[] { ':', ')' };

    Character[] smile = new Character[face.length];
    for (int i = 0; i < face.length; i++) {
        smile[i] = face[i];
    }
    
    System.out.println(smile);
}