Here is a simple Point class and a partially completed Circle class. class Point

ID: 3763427 • Letter: H

Question

 Here is a simple Point class and a partially completed Circle class.     class Point    {       private double x, y;        public Point(double x, double y)       {  this.x = x;          this.y = y;       }        public double getX() { return x; }       public double getY() { return y; }       public void setX(double x) { this.x = x; }       public void setY(double y) { this.y = y; }    }     class Circle    {       private Point c;   // center       private double r;  // radius        public Circle(double x, double y, double r)       {          }         public Circle(Point c, double r)       {          }        public Circle(Point c)       {  this.r = 1.0;          this.c = c;       }        public boolean equals(Circle roundThing)       {          }        // more stuff    }   (a) The third constructor in Circle has a "privacy leak". Explain why. Hint: Consider the following code.     Point p = new Point(1,2);    Circle c = new Circle(p);    p.setX(100);   (b) Complete the first two Circle constructors. Be sure to avoid another "privacy leak".   (c) Complete the equals method in the Circle class.

Explanation / Answer

Required solution:

(a) The third constructor in Circle has a "privacy leak". Explain why. Hint: Consider the following code.

Point p = new Point(1,2);
Circle c = new Circle(p);
p.setX(100);

observe the above example
Circle object is created with point (1,2) but point x was changed to 100
results in change of x in Circle as well

(b) Complete the first two Circle constructors. Be sure to avoid another "privacy leak".
creating new object avoid privacy leak
public Circle(double x, double y, double r)
{
this.r=r;
this.c=new Point(x,y);
}

public Circle(Point c, double r)
{
this.c=new Point(c.x,c.y);
this.r=r;
}

(c) Complete the equals method in the Circle class.
public boolean equals(Circle roundThing) {
       return this.r == roundThing.r
               && (this.c != null && roundThing.c != null
                       && this.c.getX() == roundThing.c.getX() && this.c
                       .getY() == roundThing.c.getY());
   }

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Here is a simple Point class and a partially completed Circle class. class Point

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