Collection is a group of [differently typed] objects.  [primitives need wrappers]
java.util
algorithms of java.util.Collections manipulate the collection.
Iterators loop over objects of a collection.
similar to C++'s STL  (C++: "container",  Java: "collection")


List of objects.  indexed
Set of unique objects.  can't add duplicates (equals() to determine equality).
Map of name/value pairs (key/value pairs)


Class name	features      interface it implements	ordered	sorted
----------	-------	      ----------------------	-------	------

ArrayList	dynamic array		List		yes	no
		fast iteration
		slow insert/delete
		fast random access

LinkedList	fast insert/delete	List		yes	no
		good for stack, queue
		slower iteration 


HashSet		unpredictable iteration	Set		no	no

LinkedHashSet	ordered by insertion	Set		yes	no
		(default), or by last
		access

TreeSet		ascending order		Set		yes	yes
								(natural
								order)

HashMap		fast insert/delete	Map		no	no

LinkedHashMap	ordered by insertion	Map		yes	no
		or last access
		fast iteration

TreeMap					Map		yes	yes
								(natural
								order

user-defined class needs equals() and hashcode() overridden for
HashSet and HashMap.
needs a Comparator if sort() or TreeSet or TreeMap

***********************
Methods
all Lists and Sets:
  add(object)
  addAll(collection)
  remove(object)
  clear()
  contains(object)   returns boolean
  isEmpty()
  size()
  iterator()         returns Iterator
  toArray()          returns array of Object

all Lists:
  add(index,object)   insert before index
  set(index,object)   overwrite
  get(index)          returns Object
  indexOf(object)
  remove(index)

SortedSet (e.g. TreeSet)
  first()
  last()

LinkedList: suitable as stack (LIFO) and queue (FIFO)
  addFirst(object)
  addLast(object)
  getFirst()
  getLast()
  removeFirst()
  removeLast()

Map:
  put( key object, value object )
  remove( key object )   //key and value removed
  get( key object )      //returns value
  containsKey( key object )  //boolean
  entrySet()    //returns Set of Map.Entry  (see iteration below)

****************************

Collections algorithms (static utility methods of Collections class)
  copy(dest_list1,src_list2)
  max(collection)   returns Object
  min(collection)   returns Object
  reverse(list)
  shuffle(list)
  sort(list)

****************************

Iterator

Iterator iter = collectionObject.iterator();
while (iter.hasNext())    //not at end of collection
  iter.next()          //returns next object in the collection as Object
  iter.remove()        //removes current object
  ...


Iterator iter = mapCollection.entrySet().iterator();
while ( iter.hasNext() ) {
  entry = (Map.Entry) iter.next();
  entry.getKey()
  entry.getValue()