Java Collection (Medium)

Java Collections Framework

• The root interface for all collection classes is Collection.
• The interface that extends Collection and is used to store an ordered collection of objects is List.
• ArrayList is a class that implements the List interface and is a dynamic array that allows duplicate values.
• Vector is a class that implements the List interface, is a dynamic array, and is synchronized.
• Stack is a class that is a subclass of Vector and implements the Last-In-First-Out principle.
• LinkedList is a class that implements the List and Deque interfaces and is a linear data structure that consists of nodes instead of elements.
• Map is an interface that is not a true Collection but is fully integrated with Collections.
• Queue is an interface that extends the Collection interface and implements the First-In-First-Out principle.
• Deque is a data structure that can be used both as a queue or a stack and supports common methods like addition and deletion.
• PriorityQueue is a data structure used when we need to process objects based on priority.
• Set is a collection that does not allow duplicate elements.
• LinkedHashSet is an implementation of Set that is ordered and allows iteration through the elements in their order of insertion.
• TreeSet is an implementation of Set that provides a total ordering of the elements.
• Map is a data structure that stores data as key-value pairs and maps keys to values.

Purpose and History of Java Collections Framework

• The Java Collections Framework was introduced to provide a standardized way of working with collections.
• The purpose of the Java Collections Framework is to provide a set of classes and interfaces that can be used to work with collections of objects.
• Before the introduction of the Java Collections Framework, standard collections used were Vector, Stack, Dictionary, HashSet, and TreeSet.
• The introduction of the Java Collections Framework solved the problem of having to implement custom collections for each project.
• RandomAccess is not a class/interface defined in the Java Collections Framework.

ArrayList

• The hierarchy of the Java Collections Framework is Collection -> List -> ArrayList.
• The add() method is used to add elements to the end of an ArrayList by default.
• The syntax for creating an ArrayList object is ArrayList<> list = new ArrayList<>();.
• The get() method is used to access the element at the specified index in an ArrayList.
• The contains() method is used to check whether an ArrayList contains a specified element or not.
• The size() method is used to return the size of an ArrayList.
• The ensureCapacity() method is used to increase the capacity of an ArrayList if necessary.
• The remove() method is used to remove an element from an ArrayList at the specified index.
• The set() method is used to update an element in an ArrayList at the specified index.
• The Collections.sort() method is used to sort the elements in an ArrayList in ascending order.