Java Annotations

Annotations were a feature introduces in Java 5. By the way the current version of java is 8.

Annotations tell the compiler about additional information.

Annotations commonly used are :

@Entity
@RequestMapping

Annotations can be applied to class, method, method parameter and instance variable

JAVA and OOPS multiple choice questions Test with answeres

Since now a days the number of candidates appearing for a job has increased, companies have started keeping screening process. This screening process consist of objective questions which can be answered online. Only those candidates which score good marks in Objective questions are called for personal interviews.

This blog has multiple choice OOPS and Java  questions. It is a mix of topics like Inheritance, overriding, static, constructor etc.

Read the question and try to solve it yourself. Then you can click on the Answer button to verify your answer.


Core Java Test 1 >> Core Java Test 2 >> Exception Handling Test 3

Java Access Specifier

Java has four access specifies:

1.    Public

2.    Private

3.    Protected

4.    Default

Class

A class can be defined either as public or default. Note: default is not a keyword as public. When no access specifier is mentioned default access specifier is applied.

Java Collections : Internal Working

Java Collections:

Going for an Job Interview? be prepared with Java Collections framework. Java Collection framework is the most preferred topic by interviewers. It gives them the idea of how much effort the interviewee as taken to understand this framework and clear the interview.

And guess what, similar questions are now also asked in US for H1B visa holders, or MS post graduates looking for job.

This blog explains internal working of the Collection framework. For Interview Question on Collection refer Java Collection Interview Questions. 

For Java Interview questions for 2 to 5 years Senior Developer refer this blog.

Recently Blockchain has also made place in Java Interviews. Blockchain internally is also a Data Structure. To know more click here : Implementing Blockchain using Java

Click Here for Core Java Objective Questions and Answers

Custom implementation of Collections and Data Structure:

Internal Working of Arraylist
Internal Working of LinkedList
Internal Working of HashMap
Internal Working of TreeMap

Java Collection internally uses the primitive and core elements like Arrays and datastructures like  Linked List, Tree etc. So if you are asked a question to explain the internal working of any of the Collection classes, don't be surprised. Be it an interview for an Junior Java developer or even for an Architect, Java Collection is always something that you will have on you plate.

Java provides many collection classes that can be used to store data. Knowing which collection class to use for best performance and optimum result is the key.

First the basics.
Below two image shows the complete hierarchy of interfaces and classes present in the Collection framework.

The Collections come in basic four flavors:
Lists : List of things ( Classes that implement List Interface)
Sets : Unique things ( Classes that implement Set Interface)
Maps : Things with unique id ( Classes that implement Map Interface)
Queues : Things arranged in order ( Classes that implement Queue Interface)

The blue ones are the Interfaces and the red ones are the implementation classes

Below is Map. A map is a special type of collection.

          Below table shows the different concrete classes implementing these interfaces

Maps	Sets	Lists	Queues	Utilities
HashMap	HashSet	ArrayList	PriorityQueue	Collections
Hashtable	LinkedHashSet	Vector		Arrays
TreeMap	TreeSet	LinkedList
LinkedHashMap