TestCircle.java

public class TestCircle {  // Save as "TestCircle.java"
   public static void main(String[] args) {
      // Declare an instance of Circle class called c1.
      // Construct the instance c1 by invoking the "default" constructor
      // which sets its radius and color to their default value.
      Circle c1 = new Circle();
      // Invoke public methods on instance c1, via dot operator.
      /*System.out.println(c1.radius);
      Not visable to the program*/
      System.out.println("The circle has radius of " 
         + c1.getRadius() + " and area of " + c1.getArea());
   
      // Declare an instance of class circle called c2.
      // Construct the instance c2 by invoking the second constructor
      // with the given radius and default color.
      Circle c2 = new Circle(2.0);
      // Invoke public methods on instance c2, via dot operator.
      System.out.println("The circle has radius of " 
         + c2.getRadius() + " and area of " + c2.getArea());
      Circle c3 = new Circle(3.0, "red");
      System.out.println("The circle has radius of " 
         + c3.getRadius() + " and area of " + c3.getArea() + " and is " + c3.getColor());
         Circle c4 = new Circle(2.0, "red");   // construct an instance of Circle
         c4.setRadius(5.0);          // change radius
         System.out.println("radius is: " + c4.getRadius()); // Print radius via getter
         c4.setColor("blue");        // Change color
         System.out.println("color is: " + c4.getColor());   // Print color via getter
         
         // You cannot do the following because setRadius() returns void,
         // which cannot be printed.
         //System.out.println(c4.setRadius(4.0));
    Circle c = new Circle(5.0);
    System.out.println(c.toString());   // explicit call
    Circle c6 = new Circle(1.2);
System.out.println(c6.toString());  // explicit call
System.out.println(c6);             // println() calls toString() implicitly, same as above
System.out.println("Operator '+' invokes toString() too: " + c6);  // '+' invokes toString() too
   }
}