Introduction to Microservice Architecture Using SpringBoot - Part 1

Collections in Java

The Collection in Java is a framework that provides an architecture to store and manipulate the group of objects.Java Collections can achieve all the operations that you perform on a data such as searching, sorting, insertion, manipulation, and deletion.

Java Collection means a single unit of objects. Java Collection framework provides many interfaces (Set, List, Queue, Deque) and classes (ArrayList, Vector, LinkedList, PriorityQueue, HashSet, LinkedHashSet, TreeSet).

Java Collection Interface

The Collection interface is the root interface of the Java collections framework.

There is no direct implementation of this interface. However, it is implemented through its subinterfaces like List, Set, and Queue.

ArrayList

The ArrayList class extends AbstractList and implements the List interface. ArrayList supports dynamic arrays that can grow as needed.

LinkedList 

Linked List is a part of the Collection framework present in java.util package. This class is an implementation of the LinkedList data structure which is a linear data structure where the elements are not stored in contiguous locations and every element is a separate object with a data part and address part.

Accessing a Java Collection via a Iterator

Step - 1: Create an object of the Iterator by calling collection.itertor( ) method.

Step - 2: Use the method hasNext( ) to access to check does the collection has the next element. (Use a loop).

Step - 3: Use the method next( ) to access each element from the collection. (use inside the loop).

 Using for-Each loop − Use a foreach loop and access the array using object.  Using Iterator −   Use a foreach loop and access the array using object.