$1.$ Assume the Circle class from the classroom. The Comparable interface enables an

object to compare itself with another object of the same type. It requires a single

method to be implemented, the public int compareTo$($Circle circle$).$ This

method expects another object of the same type $($Circle$)$ and compares it to this

object, the one that the method is being called upon.

$!$"Write the class declaration $($not the entire body of the class!$)$ so that it

implements the Comparable interface.

$!$"Implement the compareTo method. If the radius of the circle is less than

this object's radius return $1$; return $0$ if both values are the same; return

$-1$ if circle's radius is greater than this object's.

$2.$ Extend the class Container given below.

abstract class Container $\{$

abstract boolean isFull$()$;

abstract void add$($int volume$)$;

abstract void remove$($int volume$)$;

$\}$

$3.$ Implement the interface Fillable below.

public interface Fillable $\{$

boolean isFull$()$;

void add$($int volume$)$;

void remove$($int volume$)$;

$\}$