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.

Write two static methods in the following Bytes class.

The first should take an int and return an array of 4 bytes.

The second should take that array of 4 bytes and give back the original int.

There are a few ways to do this, but you only pass the test if you can do a "full round trip."

class Bytes {
    static int toInt(byte[] bytes) {
        // CODE HERE
    }
    static byte[] toBytes(int value) {
        // CODE HERE
    }
}

class Main {
    void main() {
        int i = 172089379;

        byte[] bs = Bytes.toBytes(i);

        // 172089379
        IO.println(Bytes.fromInt(bs));
    }
}

Challenge 2.

Turn the String "hello world" into a short[]. Print the contents of this short[] and then turn it back into a String.

class Main {
    void main() {
        String s = "hello world";

        short[] shorts;

        // CODE HERE

        String roundTripped;

        // CODE HERE
    }
}

Challenge 3.

Make a class named UnsignedInteger. It should wrap up an int such that all operations on it are performed using the appropriate unsigned specific methods when needed.

At a minimum:

• Implement toString so that the unsigned representation is used
• Implement equals and hashCode
• Implement plus and minus
• Implement the Comparable<UnsignedInteger> interface.

// CODE HERE

class Main {
    void main() {
        var i = new UnsignedInteger(0);
        IO.println(i.minus(new UnsignedInteger(1)));
    }
}

Challenge 4.

Convert this program to use float instead of double.

class Main {
    void main() {
        double radius = Double.parseDouble(
            IO.readln("What is the radius of the circle? ")
        );
        double pi = 3.14;
        double circumference = 2 * pi * radius;

        IO.println("Circumference: " + circumference);
    }
}