• Homework Review
• Collection
• List
• Set
• Map
• Homework Overview

• Collection represent a collection of objects. 
  
• Lists are ordered collection of objects.
• Sets are un-ordered collection of unique objects.
• Map contains associations between a key object and value object.

• Typical methods on collections are:
• get size of collection
• add, remove, get an object
• Collections can be navigated using iterators

 public interface Iterator<E> {
     boolean hasNext();
     E next();
     void remove(); //optional
 }

• Most commonly used implementations:
•  ArrayList
• LinkedList
• Stack
• Vector
• Unlike arrays, List capacities are dynamic.
• Lists contain only Objects, not primitives. 
• Any primitives added will be autoboxed.

 public static void main (String[] args) {
     List<String> names = new ArrayList<String>();
     names.add("John");
     names.add("Jane");
     names.add("Dan");
     names.add("Suzie");
     for(String name : names) {
          System.out.println(name);
     }
 }

• List elements can be removed using the remove() method

 names.remove("John");

• List elements can be added using the add() method

 names.add("John");

• Count of List elements can be determined using size().

 int size = names.size();

• An element can be found in a collection by using:
• contains(Object o) : returns true/false
• indexOf(Object o) : returns the index or -1 if not found

 boolean found = names.contains("John");
 int index = names.indexOf("John");

• sort(List<E> list) - sorts a List collection

 List<String> names = ArrayList<String>();
 ...
 Collections.sort(names);

• copy(List<E> dest, List<E> src) - copies values from one list to another.

 List<String> filledList = ArrayList<String>();
 List<String> emptyList = ArrayList<String>();
 ...
 Collections.sort(emptyList, filledList);

• Sets are iterable, un-ordered Collections
• Sets do not allow duplicates

 public static void main (String [] args) {
     Set<String> names = new HashSet<String>();
     names.add("John");
     names.add("Jane");
     System.out.println(names);
 }

• Non-iterable Collection that contains key-value pairs.
• Keys cannot have duplicates.
• Common implementations:
• HashMap
• TreeMap

 public static void main(String [] args) {
     Map<String, String> myMap = new HashMap<String, String>();
     myMap.put("John", "Seattle");
     myMap.put("Dan", "Nashville");
 }