Summary of common Java Containers (collections)

When I first came into contact with the container, I always felt a lot of things difficult. Learn to summarize, commonly used is nothing less than the following, methods do not need to remember all, remember a few key, where the red method must be remembered.

Collection
├list
│├linkedlist
│ArrayList
│└vector
│└stack
└set

Hashset
Map
├hashtable
├HashMap 
└weakhashmap

1, Collection: (Common sub-interface set and list)

Common methods:

int size ();     boolean isEmpty ();   void Clear ();   Boolean contains (Object element);

equals Boolean Add (Object element);    Boolean remove (Object element); Boolean containsall (Collection c);

Boolean AddAll (Collection c);    Boolean RemoveAll (Collection c);   Boolean retainall (Collection c); Ask for Intersection

eg:size (): The number of elements in the container at this time; contains (object O): whether the given O value is included;

Array read fast change slow

Linked fast reading Slow

Hash search extremely fast, traverse very slow

Tree Insert/Search is fast, suitable for indexing

(1) Set: unordered and non-repeatable ; Common Implementation class: Hashset,treeset;

Unordered: The first random, and then if no other elements of the join or exit, then keep this order, different from the random;

Do not repeat: Beware of "object" problems, you must first override the Equals and hashcode () methods; Hashcode () determines whether two objects point to the same object;

Common method: The set interface itself does not provide additional methods, all methods are from collection;

Common Implementation classes: HashSet (), TreeSet ();

(2) List: order can be repeated; Common Implementation class: ArrayList; LinkedList;

Common methods: In addition to Collection inside the method, there are the following:

Object get (int index); Output subscript corresponding value by subscript

object Set (int index, object element);//subscript to replace the corresponding subscript value    

void Add (int index, Object element); Represents the insertion of the given O value from the index position add (Oject o);

Object Remove (int index); Delete the element that corresponds to the subscript

int indexOf (Object o); Gets the index of the first occurrence of the O value in a given container

int lastIndexOf (Object o); Gets the index of the last occurrence of a 0 value in a given container

Remove (int index); //indicates that the corresponding underlying value is removed by subscript,

Note: If the given value has an integer type, it is not removed with a specific value, but instead the following value is removed; Remove (Object o);

Note: ArrayList has two add (), remove ()? A: One method comes from collection, and the other is from its own method.    

(3) Map interface: It is a combination of k,v value, and K value can not be duplicated;

Common Implementation classes: HashMap: disorder;

TreeMap: According to the size of the K value to output;

Linkedhashmap: Output According to the order of input;

Common methods:

Object put (object key, object value);

Object get (object key); Returns the value that corresponds to the key value;

Object remove (object key);

Boolean ContainsKey (Object key); A method that contains key values that are commonly used to determine whether a user name exists

Boolean Containsvalue (Object value);

int size ();

Boolean isEmpty ();

void Putall (Map t);

void Clear ();

Keyset (): assigns the K value inside the map to the set interface;

VALUES (): Assigns the V value inside the map to the collection interface;

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Summary of common Java Containers (collections)