Example 3.13 Interface Measurable

/** An interface for methods that return
* the perimeter and area of an object.
*/
public interface Measurable
{
    /** Task: Gets the perimeter.
    * @return the perimeter */
    public double getPerimeter ();

    /** Task: Gets the area.
    * @return the area */
    public double getArea ();
} // end Measurable

Example 3.14    Interface NameInterface

/** An interface for a class of names. */
public interface NameInterface
{
    /** Task: Sets the first and last names.				
    * @param firstName a string that is the desired first name	
    * @param lastName a string that is the desired last name */    
    public void setName (String firstName, String lastName);

    /** Task: Gets the full name.					
    * @return a string containing the first and last names */	   
    public String getName ();

    public void setFirst (String firstName);
    public String getFirst ();
    
    public void setLast (String lastName);
    public String getLast ();

    public void giveLastNameTo (NameInterface aName);
    
    public String toString ();
} // end NameInterface

Example 3.28  Class Circle

public class Circle implements Comparable < Circle > , Measurable
{
    private double radius;

    // Definitions of constructors and methods are here 

    public int compareTo (Circle other)	
    {							
        int result;					
        if (this.equals (other))		
            result = 0;				
        else if (radius < other.radius)	
            result = -1;				
        else						
            result = 1;				
        return result;				
    } // compareTo					

// Version 2    

    // assumes radius is an integer				
    public int compareTo (Circle other)			
    {									
        return radius - other.radius;				
        // Note: value returned not necessarily -1 or +1	
        //       but satisfies the definition		
    } // compareTo							
}