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;
This article is from the "Not _ Heroes" blog, please be sure to keep this source http://notahero.blog.51cto.com/10306439/1673525
Summary of common Java Containers (collections)