Tag Archives: concepts

Java Interview Questions – Java Concepts

  • What are the different types of memory areas allocated by JVM?
    • Class (Method) Area – stores per-class structures like fields, method data, method code and constant pool.
    • Heap – runtime area where the actual objects reside.
    • Stack – holds local variables and partial results and plays a pivotal role in method invocation and return. For each thread created, private JVM stack is being created and maintained. It stores each method invocation in the form of a frame and its destroyed soon after the method invocation is complete.
    • Program Counter (PC) Register – it contains the currently executed Java Virtual Machine instruction.
    • Native Method Stack – contains all the native method used in the application.
  • What makes Java software-based platform to be called as “write once run anywhere”?

Because of the program being compiled into bytecode and this bytecode being run inside a runtime environment (JVM) makes this software-based platform able to run on top of other hardware-based platforms. The JVM though is platform dependent and is available for various hardware-platforms available.

  • Does Java support multiple inheritance?

Theoretically on the class level Java doesn’t support multiple inheritance to avoid complexity and with the aim of simplifying the language. Having said that using interfaces it does support multiple inheritance and is widely used.

  • What is Association, Aggregation and Composition?

I wouldn’t want to reinvent and write answer for this question, rather I would point you directly to this link here.

  • What is meant by Abstraction, Generalization, Realization and Dependency?

Again read the link here and you will get all the relevant details.

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Basic Core Java Concepts

First of all, advance bail on my behalf if my content is insignificant at this point. I thought of writing this blog post after searching through Google Trends and noting that there are good amount of search queries till now looking for these basic core java concepts.

I don’t want to split this blogs into multiple parts as i feel it wouldn’t be good for a reader to go onto various parts and would like to keep it an ever evolving blog post with full support from my readers.


My previous blogs could give some inputs in bulleted points to new Java developers as given below:-

Basic Java FAQ – Part 1

Basic Java FAQ – Part 2

Basic Java FAQ – Part 3

SCJP – Quick Notes

and finally and small mock example to check knowledge

Mock Exam

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