Type Variables

• Generic programming: creation of programming constructs that can be used with many different types
  • In Java, achieved with inheritance or with type variables
• For example:
  • Type variables: Java's ArrayList (e.g. ArrayList<String>)
  • Inheritance: LinkedList implemented in Section 20.2 can store objects of any class
• Generic class: declared with a type variable E
• The type variable denotes the element type:

  public class ArrayList<E> // could use "ElementType" instead of E
  {
     public ArrayList() { . . . }
     public void add(E element) { . . . }
     . . .
  }