Another Error

The program below will not compile. It tries to access the private instance variables of the object, and this cannot be done.

public class TestCone
{
  public static void main( String[] args ) 
  {
    Cone cone  = new Cone( 1.2, 4.56 );
    System.out.println( "cone area: " + cone.area() 
      + " volume: " + cone.volume() );

    cone.height = 4.5;         // Can't accrss
    cone.radius = 13.06;       // private members

    System.out.println( "cone area: " + cone.area() 
      + " volume: " + cone.volume() );
  }
}

One approach to this problem is to make the instance variables public. But violates the idea of modularity. A better approach is to include methods that can be used to access the variables.

Here is the full list of methods from the beginning of this chapter:

Methods

public double area() calculates and returns the area of the cone

public double volume() calculates and returns the volume of the cone

public void setHeight() changes the height of a cone

public void setRadius() changes the radius of a cone

public double getHeight() returns the height of a cone

public double getRadius() returns the radius of a cone

public String toString() returns a reference to a String that describes this object

Answer:

Another Error

QUESTION 20: