Rectangle

• Class header
• Instance variables
• Constructor
• Accessor: getWidth
• Method: area

Square

• Class header
• Constructor
• etc.

AddConstant

• Constructor, addTo, setConstant
• Knows constant to add

{
  AddConstant a = new AddConstant(5);
  int x;
  x = a.addTo(7); // gives x=12
  x = a.addTo(80); // gives x=85
  a.setConstant(3); // now does +3 
  x = a.addTo(7); // gives x=10
}

RainbowBug

• Straight 5 steps
• Change color: red -> green -> blue
• Repeat color changes forever

Instance variables?