A collection is an object that groups multiple elements into a single unit for storing, retrieving, manipulating and communicating data. Common Java collection interfaces include List, Set, and Map. Popular implementations are ArrayList, LinkedList, HashSet, TreeSet, HashMap and TreeMap. Collections provide benefits like reduced programming effort, increased speed and quality, interoperability of data, and software reuse.

1. Masudul Haque

2. A collection — sometimes called a container —
is simply an object that groups multiple
elements into a single unit. Collections are
used to store, retrieve, manipulate, and
communicate aggregate data.

3. 
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Data Structure
Interface
Implementation
Algorithm
Concurrency

4. 
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

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Jdk 1.0: Vector, Stack, Dictionary, Hashtable,
Enumeration
Jdk 1.2: List, Set, Map, ArrayList, LinkedList,
HashSet, TreeSet, HashMap, WeakHashMap
Jdk 1.4: RandomAccess, IdentityHashMap,
LinkedHashMap
Jdk 1.5: Queue, java.util.concurrent
Jdk 1.6: Deque, NavigableSet/Map
Jdk 1.7: TransferQueue, LinkedTransferQueue

5. 
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Reduces programming effort.
Increases programming speed and quality.
Allows interoperability of unrelated data.
Reduces learning effort.
Reduces effort of to design new APIs
Foster software reuse.

11. 
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Indexed access
Uses offset from memory address for fast
memory access
In Java - fixed size memory block with VMlevel support

12. 
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Dynamic structure made of pointers
Easy to insert and delete new elements
No indexed access

14. Think of an example with ArrayList:
List<String> listA = new ArrayList<>();
listA.add("B");
listA.add("C");
listA.add("D");
listA.add("C");
for (String string : listA) { //Iteration
if (string.equals("C")) {
listA.remove("C"); //ConcurrentModificationExp
}
}
System.out.println(listA);

15. List<String> listA = new CopyOnWriteArrayList<>();
listA.add("B");
listA.add("C");
listA.add("D");
listA.add("C");
for (String string : listA) {
if (string.equals("C")) {
listA.remove("C");
}
}
System.out.println(listA);

16. 

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Thread safe. Never throws ConcurrentModificationEception.
Copy-on-write operation.
Snapshot iterator.

17. Data
Structure
Sorting
Iterator
Null Support?
ArrayList
Array
No
Fail-fast
Yes
LinkedLIst
Linked list
No
Fail-fast
Yes
CopyOnWrite
ArrayList
Array
No
Snapshot
Yes

18. add
remove
get
contain
ArrayList
O(1)
O(n)
O(1)
O(n)
LinkedLIst
O(1)
O(1)
O(n)
O(n)
CopyOnWrite
ArrayList
O(n)
O(n)
O(1)
O(n)

19. 


Fail-fast - work on live data, but become
invalid when live data is modified
Weakly consistent - work on live data, safe,
reflect updates and deletes, but not inserts
Snapshot - work on a snapshot of the live
data, fast, safe, but possibly stale

21. 
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first() : E
last() : E
headSet(E toElem) : SortedSet<E>
subSet(E fromElem, E toElem) : SortedSet<E>
tailSet(E fromElem) : SortedSet<E>
comparator() : Comparator<? super E>

22. 
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pollFirst() : E
pollLast() : E
subSet(E from, boolean inclusive, E to, boolean inclusive) :
NavigableSet<E>
headSet(E to, boolean inclusive) : NavigableSet<E>
tailSet(E from, boolean inclusive) : NavigableSet<E>
ceiling(E e) : E
floor(E e) : E
higher(E e) : E
lower(E e) : E
descendingSet() : NavigableSet<E>
descendingIterator() : Iterator<E>

24. Data Structure
Sorting
Iterator
Nulls?
HashSet
Hash table
No
Fail-fast
Yes
LinkedHash
Set
Hash table+
Linked list
Insertion order
Fail-fast
Yes
EnumSet
Bit Vector
Natural order
Weekly
Consistent
No
TreeSet
Red-black tree
Sorted
Fail-fast
Depends
CopyOnWriteA
rraySet
Array
No
Snapshot
Yes
ConcurrentSki
pListSet
Skip list
Sorted
Weekly
Consistent
No

25. 
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Series of linked list
Reasonably fast search add and remove
Lock free implementation

26. add
contains
next
HashSet
O(1)
O(1)
O(h/n)
LinkedHash Set
O(1)
O(1)
O(1)
EnumSet
O(1)
O(1)
O(1)
TreeSet
O(log n)
O(log n)
O(log n)
CopyOnWriteArray
Set
O(n)
O(n)
O(1)
ConcurrentSkipLis
tSet
O(log n)
O(log n)
O(1)

28. Throws exception
Returns special value
Insert
add(e)
offer(e)
Remove
remove()
poll()
Examine
element()
peek()

29. Throws
exception
Special value
Blocks
Time out
Insert
add(e)
offer(e)
put(e)
offer(e,time,
unit)
Remove
remove()
poll()
take()
poll(time,
unit)
Examine
element()
peek()
Not
applicable
Not
applicable

31. 
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Balanced binary tree
Root is always highest priority
Inserts and removes cause re-balancing

32. Head:Throws Head: Special Tail: Throws
exception
value
exception
Insert
Remove
Examine
Tail: Special
value
addFirst(e)
offerFirst(e)
addLast(e)
offerLast(e)
removeFirst()
pollFirst()
removeLast()
pollLast()
getLast()
peekLast()
Stack: push
Queue: remove
Stack:pop
getFirst()
Queue: element
Queue: poll
peekFirst()
Queue:peek
Stack:peek
Queue: add
Queue: offer

33. Head
Throws
exception
Insert
addFirst(e)
Stack: push
Special value
Blocks
Time out
offerFirst(e)
putFirst(e)
offerFirst(e,
time,unit)
Queue: add
Queue: offer
takeFirst()
pollFirst(e,
time,unit)
Special value
Blocks
Time out
offerLast(e)
putLast(e)
offerLast(e,
time, unit)
Remove
removeFirst()
pollFirst()
Examine
getFirst()
peekFirst()
Queue: element
Queue:peek
Stack:peek
Tail
Throws
exception
Insert
addLast(e)
Remove
Examine
Queue: remove
Stack: push
removeLast()
Queue: remove
Stack:pop
getLast()
Queue: element
Queue: poll
pollLast()
Queue: poll
peekLast()
Queue:peek
Stack:peek
Queue: put
takeLast()
Queue: offer
pollLast(e,
time, unit)

37. Producers wait for consumers to receive
elements. Useful for message passing. Similar
to a broader version of SynchronousQueue.
hasWaitingConsumer() : boolean
getWaitingConsumerCount() : int
transfer(E e)
tryTransfer(E e) : boolean
tryTransfer(E e, long timeout, TimeUnit unit) :
boolean

39. put(E key, V value) : V
putAll(Map<? extends K, ? extends V> m)
remove(Object key) : V
clear()
containsKey(Object key) : boolean
containsValue(Object value) : boolean
isEmpty() : boolean
size() : int
get(Object key) : V
entrySet() : Set<Map.Entry<K,V>>
keySet() : Set<K>
values() : Collection<V>

40. firstKey() : K
lastKey() : K
headMap(K to) : SortedMap<K, V>
subMap(K from, K to) : SortedMap<K, V>
tailMap(K from) : SortedMap<K, V>
comparator() : Comparator<? super K>

41. firstEntry() : Map.Entry<K,V>
lastEntry() : Map.Entry<K,V>
ceilingEntry(K key) : Map.Entry<K,V>
ceilingKey(K key) : K
floorEntry(K key) : Map.Entry<K,V>
floorKey(K key) : K
higherEntry(K key) : Map.Entry<K,V>
higherKey(K key) : K
lowerEntry() : Map.Entry<K,V>
lowerEntry(K key) : K
navigableKeySet() : NavigableSet<K>
pollFirstEntry() : Map.Entry<K,V>
pollLastEntry() : Map.Entry<K,V>
headMap(K to, boolean inclusive) : NavigableMap<K,V>
subMap(K from, boolean fromInc, K to, boolean toInc) : NavigableMap<K,V>
tailMap(K from, boolean inclusive) : NavigableMap<K,V>
descendingKeySet() : NavigableSet<K>
descendingMap() : NavigableMap<K,V>

42. putIfAbsent(K key, V value) : V
remove(Object key, Object value) : boolean
replace(K key, V value) : V
replace(K key, V oldValue, V newValue) : boolean