Introduction to Java Virtual Machine (JVM) Internals

Have you ever thought about what happens behind the scenes when you run a Java program? It’s the magic of Java Virtual Machine (JVM).

JVM is responsible for the smooth execution of your Java program. This piece of software acts as a virtual computer, making sure your Java code is run on any device. But JVM does a lot more than that!

In this article, you’ll get to learn about different components of JVM and their internal workings. So, let’s begin!

Introduction to Java Virtual Machine (JVM)

JVM is a very important part of the Java programming language. It’s because, with the help of JVM, you can run the same program on different computers without making any alterations. Due to JVM, Java programming has become a lot more versatile and impactful. The JVM plays a crucial role in enabling Java applications to interact withHTTPS and keep your data secure.

JVM is basically a bridge between the Java code and the computer it’s running on. The Java program is first compiled into bytecode so that the JVM can understand it. This bytecode is then translated into machine code, which the computer can execute.

JVM is known for its platform independence. With its help, Java applications can run on different devices like a laptop, server, or mobile. Furthermore, JVM also handles memory management, code verification, loading classes, and managing threads.

The main components of JVM architecture

The main components of JVM architecture are as follows:

  • Class loader subsystem
  • Runtime data areas
  • Execution engine

What is the class loader subsystem?

Let’s say your Java program is all set to be executed with all the classes organized in distinct files. But how will your computer know where to locate those files? That’s where the class loader subsystem comes into the picture.

Here’s how the class loader subsystem works:

  • Loading classes

Its main job is to load class files into memory when the Java program needs them. Alongside this, it also finds those files, whether they are on your computer or on a remote server.

  • Verifying classes

Once the file is found, the class loader verifies the file. It also looks for any probable bugs or errors.

  • Linking classes

After the class loader approves the files, the class is linked with the program.

  • Initializing classes

At last, the class loader initializes the static variables or blocks of code.

crucial parts of JVM

Exploring JVM runtime data areas

Once the Java program is all set to be executed, there are different memory areas that are obstructing it from running smoothly. Some of those memory areas are as follows:

  • Method area

All the class-related things are present here—for example, method code, field data, and class-level information.

  • Heap

It’s one of the main areas where the objects are created. Whenever your Java program needs a new object like a string or integer, it finds a place in the heap.

  • Java stacks

Whenever a method gets called, a new entry is added to the Java stacks.

  • Program counter register

The PC register keeps note of the instructions for executing the next while running the Java program.

  • Native method stack

The native methods written in languages like C or C++ find a place in these stacks.

What is the role of the execution engine?

The execution engine is one of the crucial parts of JVM. Due to this, your Java code is able to run on the computer. You can understand how it works by going through the points below:

  • Interpreter

With this tool, your Java bytecode(the code your Java program gets translated into) is executed. It’s not that fast, but it completes the interpretation appropriately.

  • Just-in-time(JIT) compiler

The JIT compiler takes your bytecode and converts it into a native machine code. With its help, your Java program runs a lot faster and smoother.

  • Garbage collector

It plays a significant role in ensuring everything runs smoothly. Java program creates and destroys several objects while executing. The garbage collector comes as a saviour and reclaims memory from objects that are not needed anymore.


JVM is the unsung hero responsible for the proper execution of your Java programs. In fact, it has provided a lot of new opportunities for Java developers in terms of what they can accomplish as a final result of their program execution.

So, the next time you are executing a Java program, know that it’s happening all because of Java Virtual Machine. Java programming has become a lot more flexible and accessible due to JVM.



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