What are the Concepts must know a 4 years Experienced Core Java DeveloperDev

In this post you will know what are the skills or concepts should know as a core java developer for 4 years of experienced. Core java is the language that means this is the base for all java related technologies and frameworks, and as you have 4 years of experience, you have a strong knowledge on internals with practical examples scenario based.

Lets start the main topics

1.OOPS:

• Interface and Abstract class , which situation what to use with scenario
• Abstraction and Encapsulation with real use cases
• When to use inheritance, when to use Interface
• Loose coupling and method overloading and overriding(Deep concept) with real time use cases
• constructors with super()., different combinations with static block and non static block
• Grip on static ,final key words
• Static and non static member control flow

2.Exception Handling:

• What is exception and error not theoretically definition like school going kids, you have to explain from your experience.
• Basics of try,catch finally
• throw,throws
• Exception propagation.
• Understanding the Exception hierarchy.
• Understand the Exception based on method overriding.

3.MultiThreading:

• Basics of Thread
• Ways of creating thread, Extending from Thraed class, implementing from runnable interface.
• sleep, join,yield methods with practical implementation knowledge,
• Thread class methods and object class methods like wait, notify, notifyall
• Concepts of parallelism , Synchronization
• producer consumer problems
• concurrent collection

4.Collections frame work with generics:

• Hierarchy of Collections and Map
• Grip on Collections provide classes and the interfaces, where to choose which collection having a strong knowledge.
• Grip on Map provide interfaces and classes,
• Having the sound knowledge of Internals of Map,Set,List
• Implementations of hashCode() method and equals method.
• sound knowledge of cursor objects.
• Good knowledge of Comparable and Comparator interface, where to choose which interface

5.Inner classes:

• Basics of inner classes
• Anonymous inner classes , and where to use with real time use cases.

6.String,StringBuffer,StringBuilder:

• immutable properties
• String pooling.
• 7.Wrapper classes:
• where to use
• How important
• Auto boxing and unboxing

8.Grabage collection:

• Basics of garbage collection.
• How to manage JVM memory for better performance.
• How to manage heap memory and permgen space.
• How to handle out of memory error.
• How to identify memory leak and how to handle.

9.Object class methods

• Hashcode and equals method implementation.

10.Date and time Api,Calander classes

Some Important Interview Questions which are repeatedly asked in Interview:

• write a program for singelton design pattern and how to avoid violation of its validity using java reflection.
• How hashmaps works internally and when is resizing done.
• Write a program to find one/two/three missing number in given series.
• How java garbage collector works in detail.
• Arraylist vs linklist.when to use stack/queue.
• Given stack array write program to convert it to queue.
• How ajax works.write equivalent jQuery.
• When we use throwable in exception. Answer is in logging.
• Factory design pattern.
• Sql query to find 2/3/nth highest.
• What are subquesries how is it diffrent from correlated query.
• Given array write optimised code to find two number such that there sum is k.
• Overloading overloading and method hiding.
• Static methods when to use
• Java enums
• Overriding rules of user defined exception
• How java classloader works.
• Write a program to count number of character occurance in words
• How hashset use hashmap internally
• Find 10th prime number.
• What are types of mapping possible in spring-MVC controller and annotation based.
• Architecture of spring MVC.
• multiple dispatcher servlet.
• implement LRU in java.
• implement producer-consumer problem.