Friday, September 10, 2021

What is Java Virtual Machine (JVM) & Its Architecture

What is JVM?

JVM is a engine that provides runtime environment to drive the Java Code or applications. It converts Java bytecode into machines language. JVM is a part of JRE(Java Run Environment). It stands for Java Virtual Machine

  • In other programming languages, the compiler produces machine code for a particular system. However, Java compiler produces code for a Virtual Machine known as Java Virtual Machine.
  • First, Java code is complied into bytecode. This bytecode gets interpreted on different machines
  • Between host system and Java source, Bytecode is an intermediary language.
  • JVM is responsible for allocating memory space.

In this tutorial, you will learn-

  • What is JVM?
  • JVM Architecture
  • Software Code Compilation & Execution process
  • C code Compilation and Execution process
  • Java code Compilation and Execution process
  • Why is Java both interpreted and Compiled Language?
  • Why is Java slow?

JVM Architecture

Let’s understand the Architecture of JVM. It contains classloader, memory area, execution engine etc.

1) ClassLoader

The class loader is a subsystem used for loading class files. It performs three major functions viz. Loading, Linking, and Initialization.

2) Method Area

JVM Method Area stores class structures like metadata, the constant runtime pool, and the code for methods.

3) Heap

All the Objects, their related instance variables, and arrays are stored in the heap. This memory is common and shared across multiple threads.

4) JVM language Stacks

Java language Stacks store local variables, and it’s partial results. Each thread has its own JVM stack, created simultaneously as the thread is created. A new frame is created whenever a method is invoked, and it is deleted when method invocation process is complete.

5) PC Registers

PC register store the address of the Java virtual machine instruction which is currently executing. In Java, each thread has its separate PC register.

6) Native Method Stacks

Native method stacks hold the instruction of native code depends on the native library. It is written in another language instead of Java.

7) Execution Engine

It is a type of software used to test hardware, software, or complete systems. The test execution engine never carries any information about the tested product.

8) Native Method interface

The Native Method Interface is a programming framework. It allows Java code which is running in a JVM to call by libraries and native applications.

9) Native Method Libraries

Native Libraries is a collection of the Native Libraries(C, C++) which are needed by the Execution Engine.

Software Code Compilation & Execution process

In order to write and execute a software program, you need the following

1) Editor – To type your program into, a notepad could be used for this

2) Compiler – To convert your high language program into native machine code

3) Linker – To combine different program files reference in your main program together.

4) Loader – To load the files from your secondary storage device like Hard Disk, Flash Drive, CD into RAM for execution. The loading is automatically done when you execute your code.

5) Execution – Actual execution of the code which is handled by your OS & processor.

With this background, refer the following video & learn the working and architecture of the Java Virtual Machine.

C code Compilation and Execution process

To understand the Java compiling process in Java. Let’s first take a quick look to compiling and linking process in C.

Suppose in the main, you have called two function f1 and f2. The main function is stored in file a1.c.

Function f1 is stored in a file a2.c

Function f2 is stored in a file a3.c

All these files, i.e., a1.c, a2.c, and a3.c, is fed to the compiler. Whose output is the corresponding object files which are the machine code.

The next step is integrating all these object files into a single .exe file with the help of linker. The linker will club all these files together and produces the .exe file.

During program run, a loader program will load a.exe into the RAM for the execution.

Java code Compilation and Execution in Java VM

Let’s look at the process for JAVA. In your main, you have two methods f1 and f2.

  • The main method is stored in file
  • f1 is stored in a file as
  • f2 is stored in a file as

The compiler will compile the three files and produces 3 corresponding .class file which consists of BYTE code. Unlike C, no linking is done .

The Java VM or Java Virtual Machine resides on the RAM. During execution, using the class loader the class files are brought on the RAM. The BYTE code is verified for any security breaches.

Next, the execution engine will convert the Bytecode into Native machine code. This is just in time compiling. It is one of the main reason why Java is comparatively slow.

NOTE: JIT or Just-in-time compiler is the part of the Java Virtual Machine (JVM). It interprets part of the Byte Code that has similar functionality at the same time.

Why is Java both Interpreted and Compiled Language?

Programming languages are classified as

  • Higher Level Language Ex. C++, Java
  • Middle-Level Languages Ex. C
  • Low-Level Language Ex Assembly
  • finally the lowest level as the Machine Language.

compiler is a program which converts a program from one level of language to another. Example conversion of C++ program into machine code.

The java compiler converts high-level java code into bytecode (which is also a type of machine code).

An interpreter is a program which converts a program at one level to another programming language at the same level. Example conversion of Java program into C++

In Java, the Just In Time Code generator converts the bytecode into the native machine code which are at the same programming levels.

Hence, Java is both compiled as well as interpreted language.

Why is Java slow?

The two main reasons behind the slowness of Java are

  1. Dynamic Linking: Unlike C, linking is done at run-time, every time the program is run in Java.
  2. Run-time Interpreter: The conversion of byte code into native machine code is done at run-time in Java which furthers slows down the speed

However, the latest version of Java has addressed the performance bottlenecks to a great extent.

Summary :

  • JVM or Java Virtual Machine is the engine that drives the Java Code. It converts Java bytecode into machines language.
  • In JVM, Java code is compiled to bytecode. This bytecode gets interpreted on different machines
  • JIT or Just-in-time compiler is the part of the Java Virtual Machine (JVM). It is used to speed up the execution time
  • In comparison to other compiler machines, Java may be slow in execution.

Thanks for Reading 

Sunday, June 13, 2021

Top Certifications in 2021

We all know that Post COVID , most of the industries has started moving to digital era and in this digital transformation, we have many new opportunities in coming future. 

When companies started working remotely, Most toughest thing is to find the right resource and right skill set. Most of the companies has tie up with different resource firm where they hire the resource on contract basis first and then make full time employment offer for them OR companies now a days also started giving more preferences to certified resources by default , it gives them the confidence that the certification can somewhat justify someones skill sets.

Today I will discuss about Most demanding certification program in 2021 which can definitely help you to find a better job for you.

Before I go further , I would like to recommend SPOTO IT Certification for any certification exam preparation.If you are looking for some certifications , you can definitely check this website and can look for the training or exam preparation resources you are looking for.

1) PMP - PMP stands for Project Management Professional , as the word suggest , it is now a day very high in demand and most of the projects going to digitalized and Companies need Resources who can actually make sure that there project should be successfully delivered. so The Certification is internationally recognised which can make your bright in group of peoples of same skill set.
Learn more about What is PMP Certification.

2)AWS Certifications-If you have heard about Cloud , you definitely have heard about AWS as well , AWS stands for Amazon web service. AWS itself has so many Certification and because companies now host their data on cloud , the most loved and most preferred cloud service provider is AWS because of its vast managed services and unique billing system model. AWS is hot in market and if you are planning to become a cloud engineer , I would recommend you to go and take any AWS certification. You can actually go to SPOTO IT Certification where you can find AWS Dumps which will helpful for you to pass the exam.

3)CCIE- Ever green in market is Cisco certification why ? Because networking is the base of every company and when we talk about Networking , CISCO is world no. 1 Networking company. this is the only certification which 90-100% ensure that you will definetely get the Job after doing it as it is very tough to crack and it ensure that the one who crack it should sharpen his/her knowledge.

BTW CCIE stands for Cisco Certified Internetwork Expert. You can directly go to here and can look for dumps.

4) Microsoft Certifications-Microsoft is one of the most known IT Company in the world and in its certifications are always considered as one of the most valuable in IT Ecosystem. There are so many Certifications as below
There are so many certifications of microsoft which you can go for, You can check all the certification at this URL.

There are some of the Important URLs you can go through while you are preparing about any certifications.

I hope you will find these certification helpful for your next phase in job.
If you have any issue you can leave us a comment we will definitely try to help you.

Thanks for reading