Poly morphism

1
Poly morphism

• many forms

2
Why is this such a big deal?

• private IGeometry calc // supertype
• userInput JOptionPane.showInputDialog("1-sphere
  2-cube 3-pyramid 4-Quit")
• x Integer.parseInt( userInput )
• if (x 1)
• calc new Sphere() // subtype
• else if (x 2)
• calc new Cube() // subtype
• else if (x 3)
• calc new Pyramid() // subtype
• else
• System.exit(0)

3
because

• the object is chosen in real time
• it brings along with it, specific methods

4
the methods

• System.out.println( calc.perimeter() " feet")
• System.out.println( calc.area() " sq. ft." )
• System.out.println( calc.volume() " cubic ft."
  )
• THIS CODE STAYS THE SAME NO MATTER WHICH OBJECT
  IS INSTANTIATED
• PEOPLE CAN WRITE NEW IGeometry CLASSES AND THEY
  FIT RIGHT IN

5
what makes this possible?

• private IGeometry calc
• calc new Sphere( )
• or
• calc new Cube( )
• "A subtype may be substituted for a supertype
  anywhere".