Need Help writing a test code using J Unit for this following JAVA Class

package shapes;

import java.awt.Color; import java.awt.geom.Point2D; import java.util.Objects;

/** * Represents a circle. * *

Invariant: * myRadius must be greater than zero * AND myCenter must not be null * AND myColor must not be null

* * @author Ricky * @version 2.5 */ public class Circle {

// class constants

/** * A default radius to use when no other value is specified - (1.0 - a unit circle). */ private static final double DEFAULT_RADIUS = 1.0; // unit circle

/** * A default Point for the center of a Circle - (0.0, 0.0) the coordinate system origin. */ private static final Point2D DEFAULT_CENTER = new Point2D.Double(0.0, 0.0); // origin

/** * A default Color to use when no other Color is specified - Color.BLACK. */ private static final Color DEFAULT_COLOR = Color.BLACK;

// instance fields

/** * The radius of this Circle. */ private double myRadius;

/** * The center of this Circle. */ private Point2D myCenter; // Note that java.awt.Point is mutable

/** * The color of this Circle. */ private Color myColor;

// constructors

/** * Constructs a Circle with the specified radius, location, and color. * *

Precondition: The parameters must not violate the class invariant. * That is, theRadius must be greater than zero * AND theCenter must not be null * AND theColor must not be null

* * @param theRadius the radius to assign to this Circle * @param theCenter the center point to assign to this Circle * @param theColor the color to assign to this Circle * @throws IllegalArgumentException if theRadius is less than or equal to zero * @throws NullPointerException if theCenter is null OR theColor is null */ public Circle(final double theRadius, final Point2D theCenter, final Color theColor) {

if (theRadius <= 0) { throw new IllegalArgumentException("The radius must be a positive value!"); }

myRadius = theRadius; /* * Note that the Objects class and requireNonNull() were added to Java in version 7. * The method will throw an exception if the parameter passed to the method is null. * This simplifies the code by eliminating the need for an if / else test * and an explicit throws statement. */ myColor = Objects.requireNonNull(theColor); // We must make a defensive copy of the mutable Point parameter // to avoid an encapsulation violation. // So, we must NOT simply write myCenter = theCenter! // One way to make a defensive copy is to use a copy constructor if the class has one. // Unfortunately Point2D.Double does not have a copy constructor. // Another way is to use an overloaded constructor: myCenter = new Point2D.Double(theCenter.getX(), theCenter.getY()); // OR // We can use a no argument constructor and then use setter(s). //myCenter = new Point2D.Double(); // creates Point at (0, 0) //myCenter.setLocation(theCenter); // OR // We can use the clone() method if the class we want to copy implements Cloneable. // Point2D.Double does implement Cloneable, so this works also. //myCenter = (Point2D) Objects.requireNonNull(theCenter).clone(); }

/** * Constructs a black unit circle centered at the origin. */ public Circle() { this(DEFAULT_RADIUS, DEFAULT_CENTER, DEFAULT_COLOR); }

// instance methods // 'mutators', sometimes called 'commands', or sometimes called 'setters'

/** * Sets the radius of this Circle to the specified value. * *

Precondition: theRadius must be greater than zero

*

Postcondition: this Circle will be assigned the specified radius

* * @param theRadius the radius value to assign to this Circle * @throws IllegalArgumentException if theRadius is less than or equal to zero */ public final void setRadius(final double theRadius) {

if (theRadius <= 0) { throw new IllegalArgumentException(); } myRadius = theRadius; }

/** * Sets the location of the center of this Circle to the specified point. * *

Precondition: thePoint must not be null

*

Postcondition: this Circle will be assigned the specified center Point

* * @param thePoint the center value to assign to this Circle * @throws NullPointerException if thePoint is null */ public final void setCenter(final Point2D thePoint) { // make a defensive copy of the mutable Point parameter // to avoid an encapsulation violation myCenter = (Point2D) Objects.requireNonNull(thePoint).clone(); }

/** * Sets the Color of this Circle to the specified value. * *

Precondition: theColor must not be null

*

Postcondition: this Circle will be assigned the specified Color

* * @param theColor the Color value to assign to this Circle * @throws NullPointerException if theColor is null */ public final void setColor(final Color theColor) {

myColor = Objects.requireNonNull(theColor); }

// 'accessors', sometimes called 'queries', or sometimes called 'getters'

/** * Returns the radius of this Circle. * * @return the radius of this Circle */ public final double getRadius() { return myRadius; }

/** * Returns the center Point of this Circle. * * @return the center Point of this Circle */ public final Point2D getCenter() {

// return a defensive copy of the mutable Point field // to avoid an encapsulation violation return new Point2D.Double(myCenter.getX(), myCenter.getY()); // OR //return (Point2D) myCenter.clone(); }

/** * Returns the Color of this Circle. * * @return the Color of this Circle */ public final Color getColor() { return myColor; }

/** * Calculates and returns the diameter of this Circle. * * @return The diameter of this Circle */ public double calculateDiameter() { return 2 * myRadius; }

/** * Calculates and returns the circumference of this Circle. * * @return the circumference of this Circle */ public double calculateCircumference() { return Math.PI * calculateDiameter(); }

/** * Calculates and returns the area of this Circle. * * @return the area of this Circle */ public double calculateArea() { return 2 * myRadius * Math.PI; } // overridden methods from class Object

/** * {@inheritDoc} * * The String representation of this Circle will be formatted as follows: * Circle [radius=(current value), center=(current value), color=(current value)]. */ @Override public String toString() { final StringBuilder builder = new StringBuilder(128); // default initial size = 16 builder.append(getClass().getSimpleName()); // the class name without the package name builder.append(" [radius="); builder.append(String.format("%.2f", myRadius)); builder.append(", center="); builder.append(myCenter); builder.append(", color="); builder.append(myColor); builder.append(']'); return builder.toString(); }

}