Core Java Collections Tutorials for beginners

Java Collection Framework is one of the most important and widely used framework by Java Developers.  Java Collection Framework is a collection or can be called as a container that groups multiple elements together to store, manipulate and communicate the aggregated data. 

We can also say that the Java Collection Framework is an unified architecture to store and manipulate collections. The Java Collection Framework contains:

  • Interfaces
  • Implementation
  • Algorithms

How Java Collections Framework benefits developers ?

The Java Collection Framework provides the below given advantages:

  • Java Collections Framework provides useful data structures and algorithms which helps in reducing the overall programming effort
  • Java Collections Framework provides interfaces which are interchangeable based on collections implementation and provides high quality data structures and algorithms which provides fast program execution
  • Java Collections Framework can be used among non related API integration using collections and thus allows interoperability
  • Java Collections Framework reduces the overall effort to design new APIs
  • The newly added algorithms reuses the Current Collections Framework interfaces and implementation

Interfaces in Java Collection Framework

The interfaces in the Java Collection Framework define the baseline to encapsulate different types of collections.

The below given diagram depicts the collection interfaces in java. Collections is the root hierarchy and is used by all the group of objects i.e. elements of the collections. The Collections interface is not provides for the implementation although other collection interfaces use it internally to pass the collections during run time implementation

Although Map has been shown as part of Collections but it is not a pure collection interface.

Methods in Java Collection Framework

The below given are the methods supported by Java Collection Framework

MethodDescription
public boolean add(E e)allows to insert an element in collection
public boolean addAll(Collection<? extends E> c)allows to insert the specified collection elements in the invoking collection
public boolean remove(Object element)allows to remove an element from the collection
public boolean removeAll(Collection<?> c)allows to remove all the elements from the collection
default boolean removeIf(Predicate<? super E> filter)allows to remove all the elements of the collection if given condition is justified
public boolean retainAll(Collection<?> c)allows to retain all the elements of collection based on given condition
public int size()returns the collection element count
public void clear()clears all the collection elements
public boolean contains(Object element)allows to search an element in collection
public boolean containsAll(Collection<?> c)allows to search an element in collection based on given condition
public Iterator iterator()returns an iterator
public Object[] toArray()allows to convert collection into an array
public <T> T[] toArray(T[] a)returns the array after converting collection into an array
public boolean isEmpty()depicts if collection is empty
default Stream<E> parallelStream()returns parallel stream with collection as source
default Stream<E> stream()returns sequential Stream with collection as source
default Spliterator<E> spliterator()creates Spliterator for the elements in the collection
public boolean equals(Object element)allows to compare two collections.
public int hashCode()It returns collection hash code number
Core Java Collections Tutorials for beginners

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