//--- File: Animal.java
	interface Animal { 
	    // return the name of this animal 
	    public String getName(); 
	} 
	
// --- File: Cow.java
	public class Cow implements Animal { 
		public String getName() {
			return "I'm a cow.";
		}
	} 
	
// --- File: Zoo.java 

import java.util.ArrayList;

public class Zoo {


	public static void main(String[] args) {
		ArrayList<Cow> list = new ArrayList<Cow>();
		list.add(new Cow());
		list.add(new Cow());
		printNames(list); 
	}

	public static void printNames(ArrayList<? extends Animal> zoo) {
		 for(Animal a : zoo) {
			 a.getName();
		 }
	 }
	 
	/*
	//If instead of the above, we changed the parameter type of printNames to
	public static void printNames(ArrayList<Animal> zoo) { 
	//then the call to
	printNames(list);
    //would not work because ArrayList<Cow> NOT is-a ArrayList<Animal> even though Cow is-a Animal.
	*/
}


// --- File: SortedCollection.java

// Therefore, if you do:

interface SortedCollection <E extends Comparable<E>> {}

// ...this works, but is too restrictive.  It requires that E directly 
// implement Comparable<E>, but that’s not 
// the only way two E objects can be Comparable. 
// Solution: 

interface SortedCollectionBetter <E extends Comparable<? super E>>  {}

// This means that any superclass of E should extend Comparable