Collections in Java

Interface Java.lang.Iterable is the parent interface of the Java.util.Collection interface, but occurs later regardless of the interface Java.util.Collection interface is a hierarchical interface with the interface java.util.list&lt ; The implementation class under the E> interface allows the storage of duplicate element interfaces java.util.set<e> the implementation class under the interface does not allow the storage of repeating element classes Java.util.arraylist<e> class Java.util.LinkedList <E> class java.util.hashset<e> Class Java.util.linkedhashset<e> interface Java.util.Collection method:

Method declaration	Function description
Boolean	Add (e) ensures that this collection contains the specified element (optional action).
void	Clear () Removes all elements from this collection (optional action).
Boolean	Contains (Object o) returns True if this collection contains the specified element.
Int	Size () returns the number of elements in this collection.
Boolean	Remove (Object o) Removes a single instance of the specified element from this collection, if one exists (optional action).
Object[]	ToArray () Returns an array that contains all the elements in this collection.

Collections without fixed-length arrays have fixed-length collections that cannot store basic types (four classes of eight types) can only store their reference types "< data types to store elements >" Data types must be reference data types, not basic data types; The following is a representation of the reference data type for the 8 basic data types:

Byte	Short	Int	Long	Float	Double	Char	Boolean
Byte	Short	Integer	Long	Float	Double	Character	Boolean

Let's take a few examples to clarify how the collection is created: storing elements of type String arraylist<string> list = new arraylist<string> ();  L store data of type int arraylist<integer> list = new arraylist<integer> (); Store Phone type data arraylist<phone> list = new arraylist<phone> ();

Collections in Java