Introduction to OOP Chapter 17: The Polymorphic Variable : next previous audio real text

Pure Polymorphism

A polymorphic method (also called pure polymorphism) occurs when a polymorphic variable is used as an argument. Different effects are formed by using different types of value. 
class StringBuffer {
	String append (Object value)
		{ return append(value.toString()); }
	...
}
Different objects implement toString differently, so the effects will vary depending upon the argument.
Intro OOP, Chapter 17, Slide 08