Core Java

Are you a complete newbie to core java? Or know some basics but want to revise them and understand the concepts thoroughly? Well you are at the right place, the list or articles below explain some basic concepts in java programming language and you will find them very helpful if you are preparing for core java certification exam. Some of very important topics like strings and collections are covered in detail.

Understanding basic core java:

Strings are special and interesting:

Objects and hashcodes in core java:

  • Significance of equals method?
    • This article explains how to implement equals method in java and its necessity for comparison of objects
  • What are hashcodes?
    • This tutorial explains the concept of hashcode and hash functions in computing
  • Significance of equals and hashcode
    • The tutorial explains how to override equals and hashcode in java and why the implementation of hashcode is important if equals method is implemented

Collections and Generics:

Internal Working of Collections in Core Java:

  • Working of HashMap:
    • This article deals with Working of HashMap in Java and elaborated this with the help of an example which gives step by step analysis of the internals.
  • Working of HashMap put method:
    • The article helps understand the working of hashmap put method in java with the help of simple example and diagram
  • Working of HashMap get method:
    • The article helps understand how HashMap Get Method works with the help of a simple example demonstrated with diagram
  • Working of LinkedHashMap
    • The article describes working of LinkedHashMap along with an example and elaborative diagrams. It helps understand how it is different from HashMap.
  • Working of TreeMap:
    • The article explains working of treemap in java with the help of code example and illustrative diagrams. It gives overview of red black tree in treemap.
  • Working of Hashtable:
    • The article explains the concept of Hashtable and how it works internally based on its parameters. Hashtable is compared with HashMap for understanding.
  • Fail-fast iterator:
    • The article describes the concept of fail fast iterator in java collections framework and provides detailed explanation of fail fast iterator in ArrayList.
  • Difference between HashMap and IdentityHashMap
    • The article helps understand the concept of IdentityHashMap and explains difference between HashMap and IdentityhashMap in java collections framework.
  • Working of Collections.synchronizedMap()
    • Article explains the working of Collections.synchronizedMap and similar Collections utility methods with the help of source code and detailed explaination.


  • When should you use enumerations?
    • The articles talks about the use of enumerations in java, explains the concept of enumerations and the advantages it offers to programmers.
  • Formatting dates using SimpleDateFormat
    • The tutorial describes the use of SimpleDateFormat to format the date in desired string format and parse available strings into desired date format..
  • Marshalling and Unmarshalling

    • This tutorial shows how to convert java object into xml form and xml to object form using marshalling and unmarshalling technique in JAXB i.e. Java Architecture for XML Binding in java.
  • JAXB with collections

    • The article describes the role of polymorphism in generics in java and the shortcomings faced with it. It also explains the concept of type erasure.
The following two tabs change content below.
Prasad Kharkar is a java enthusiast and always keen to explore and learn java technologies. He is SCJP,OCPWCD, OCEJPAD and aspires to be java architect.

Latest posts by Prasad Kharkar (see all)

23 thoughts on “Core Java

  • August 25, 2014 at 8:44 pm

    hi bro… can you please explain Exception handling , Threads and in detail about Collections please bro…….

  • June 12, 2015 at 11:58 pm

    Thank u Mr.Prasad. your explanation is awesome and its the solution for my query’s.
    as previous mention can u please add threads and collections too.

  • July 10, 2015 at 2:55 pm

    Dear Mr Prasad

    i had just passed my and i start my carrier as a java developer.I want to increase my theory as well as my coding knowledge.Please help me.and tell me how i increase my logical and coding skill.
    If you have time, please give me java classes.


    • July 10, 2015 at 3:26 pm

      HI Manish, I’m glad to see your enthusiasm about java. You can go through core java tutorials first to understand basics. If you have any questions you can post here or mail me. I will be glad to help.

      • December 17, 2016 at 10:23 am

        good morning sir, I had completed my degree(…but I’m very interested in java developer side features., But i’m eligible that course or not..Present I learn core java

  • August 28, 2015 at 2:49 am

    i am new in Java sir explain about for loop and nested for loop and working of the loop. suppose i want to print a triangle shape what is working of inner and outer loop.

  • December 16, 2015 at 3:16 pm

    I have been reading all your posts here! Really good and gives better understanding on first read.
    Keep up the good work .

  • January 22, 2016 at 11:25 am

    hi Prasad thanks for your blogs.One question I have why the finalize(),clone() in Object class are declared as protected not as public…

    • June 10, 2016 at 3:57 pm

      Hey Alok the clone() method can be only called from the sub classes of same or different package, so it needs to be protected. Actually once clone() method is called it will go through all the super classes implementing clonnable until it reaches to Object class and get returned in same fashion. If it would public, it could be called from anywhere.

  • September 22, 2016 at 6:20 pm

    Hey Prasad,

    Good source of collecting info on Core java. Good job buddy.
    I would say Exception Handling and Multi Threading is something can be added here. Multi threading was/is and always be a night mare for people. If you can simplify in your way would be beneficial.


    • September 22, 2016 at 11:01 pm

      Hi Samveg, thank you for your feedback, I will definitely add those topics 🙂

  • November 10, 2016 at 6:54 pm

    Hello Prasad Sir,

    Sir in Java-Collection framework which class is perform or behave like Simple-Linked-List and Circular-Linked-List.

  • November 11, 2016 at 1:43 am

    Hello Prasad Sir,

    Sir in Java-Collection framework Stack class and Queue interface what they are internally uses like LinkedList internally uses doubly linked list to store the elements., i want to know that they are use the dynamic array or not

    Abhishek Kumar Srivastava

  • January 2, 2017 at 11:25 am

    Hi Prasad,

    Wish you happy new year 2017 🙂

  • January 2, 2017 at 11:31 am

    Please can you explain in-detail of all the oops concepts including class, object and Constructors.
    Overloading, overriding, Interface and abstraction, Exception handling
    All the above are very important concepts to learn.
    Am asking you because your explanation is very simple and easy to understand novice like me.
    Please Prasad..

    Thanks in advance

    • January 2, 2017 at 2:25 pm

      Hi Madhu, I would also like to discuss about these things. Feel free to post your questions here and I will try my best to answer 🙂

  • January 4, 2017 at 3:37 pm

    sir please post the concept thread and exceptions….

    • January 6, 2017 at 9:03 am

      Hi Chandan thank you for your comment 🙂 I will keep adding articles as I go along 🙂

  • January 9, 2017 at 11:48 pm

    Hello Sir, i just became fan of yours explanation about java. i am too much passionate about java. My request is that can u please add small small program codes of core java for practice so that we can guess the output. Because in exams most of the times questions are asked like what will b the o/p of code.

  • February 6, 2017 at 1:30 pm

    Nice article 🙂 Keep it up good work!!!


Leave a Reply

Your email address will not be published. Required fields are marked *