Generic Types

• A generic type has one or more type variables
  
• Type variables are instantiated with class or interface types
• Cannot use primitive types, e.g. no ArrayList<int>
• When defining generic classes, use type variables in definition:
  

  public class ArrayList<E>
  {
     public E get(int i) { . . . }
     public E set(int i, E newValue) { . . . }
     . . .
     private E[] elementData;
  }

• NOTE: If S a subtyoe of T, ArrayList<S> is not a subtype of ArrayList<T>.