Guide to Java Virtual Machine - JVM Working and Features

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The JVM is a translator for Java code. It takes Java code, which is written in a way that's easy for humans to understand, and turns it into code that computers can understand. In short, you can write Java code once, and it can run on many different kinds of computers, from your phone to a big server. The following tutorial will discuss all the prominent concepts of Java virtual machine in detail including the features and working of JVM.

About Java Virtual Machine

JVM takes an advanced kind of code called "Java bytecode" and turns it into something that any computer can understand. In other words, you can write a program once, and it will work on all sorts of computers, from your phone to a giant server. It's like having a universal language for computers.
 

This virtual machine tells us what the computer should be able to do, but it doesn't say exactly how to build it. So, different people can build their versions of this magical computer, but they all have to follow the blueprint to ensure they work the same way. This way, you can write a program once, and it will run on any of these computers, no matter who built it!
 

We all know JVM monitoring is like a universal language for computers. You can write a Java program on one computer, and it will work on almost any other computer that knows how to speak Java. As a result, this is because there's a special translator called the Java Virtual Machine that helps computers understand Java. When you write a Java program, you save it as a .java file. The computer then turns this file into a .class file, which is like a translated version of your program. This .class file goes through a series of steps inside the JVM to make the computer understand and run your program.

Features of Java Virtual Machine

Here, we will elaborate on the features and benefits of Java Virtual Machine. Read and go through the following section to clear all your doubts. 
 

• Platform Independence: The JVM is a universal translator for Java programs. It translates your Java code into a language that any computer can understand, regardless of its operating system or hardware.
   
• Memory Management: You don't have to worry about cleaning up the trash. The JVM will take care of memory management for you. When your Java program creates objects (like a character in a game or a data structure), the JVM allocates memory for them. When these objects are no longer needed, the JVM's garbage collector automatically frees up the memory, preventing memory leaks.
   
• Security: The JVM ensures that only trusted code can access your computer's resources. If you download a Java program from an untrusted source, the JVM will scan it for malicious code and prevent it from running if it's found to be harmful.
   
• Dynamic Loading: The JVM is a set for your Java programs. If you want to add a new feature to your Java application, you can create a new class and load it into your running program at runtime. Moreover, this allows you to update your application without recompiling and redistributing the entire program.
   
• Just-In-Time (JIT) Compilation: The first time you run a Java program, the JVM interprets the bytecode. However, for frequently executed code, the JVM can compile it into native machine code, which is much faster to execute. However, this can significantly improve the performance of your Java applications.
   
• Multithreading: The JVM is a multitasker for your Java programs. In a Java program, you can create multiple execution threads that can run concurrently. 

How to Install Java Virtual Machine?

Here are the steps for downloading Java.
 

• First, go to the Java website.
• After that, click on the "Download Java" button.
• Then, agree to the license terms and start the download.
• Next, run the downloaded file.
• At last, click "Install" and follow the on-screen instructions to complete the installation.

How Java Virtual Machine Works?

Now, we will discuss the Java virtual threads performance in detail. In other words, you will get to know it working. 

Class Loader Subsystem

 It's responsible for finding Java code files in the method area and ensuring they're organized and ready to be read.

Here's what the ClassLoader does:
 

• Finds the code: It looks for the Java code file (with the .class extension).
• Organizes the code: It puts the code into a unique place in the computer's memory called the method area.
• Creates a Class Object: It makes a note of where the code is and what it's about.

The Class Loader stores the necessary information about each Java code file:
 

• The full address of the code: The complete name of the class.
• The author of the code: The name of the class's parent class.
• Whether it's a regular class, an interface, or an enum.
• The contents of the code: Information about the variables, methods, and other parts of the code.

After organizing the code, the ClassLoader creates a Class object so you can easily find the code and read it. In addition, this Class object is like a table of contents for the Java code file. You can use it to find out the name of the class, its parent class, and what it can do.

Student s2 = new Student();

// c2 will point to same object where 

// c1 is pointing

Class c2 = s2.getClass();

System.out.println(c1==c2); // true

The System Class Loader is the main detective, but it also has two assistants: the Extension Class Loader and the Bootstrap Class Loader. When someone goes missing, the System Class Loader asks the Extension Class Loader to help search. If the Extension Class Loader can't find the person, it asks the Bootstrap Class Loader. If neither of them can find the person, the case is considered unsolved, and a "ClassNotFoundException" is raised.

Java Virtual Machine Memory

• Method area: It stores information about all the classes, their class names, and what's inside them (methods and variables). There's only one library for the whole city.
• Heap area: It's where objects live and play. There's only one park in the whole city.
• Stack area: This is the stack area. Each thread has its run-time stack that keeps track of where the car is going and what it's doing.
• PC Registers: It tells the thread where to go next. Each car has its GPS.
• Native method stacks: This is the native method stack. In addition, it stores information about the threads that are parked in the native methods.

Execution Engine

This is the bytecode. It reads the guidelines and follows the instructions to prepare the data. Moreover, These are the memory areas where the data are stored. In addition, these are the instructions that the execution engine follows.

• Interpreter: It reads the guidelines line by line and follows the instructions.
• JIT compiler: It remembers the instructions that are used often and prepares them faster.
• Garbage collector: It cleans up the unreferenced objects after the meal is finished.

Conclusion

The Java Virtual Machine (JVM) is a translator that allows Java programs to speak a universal language. Moving ahead, it bridges the gap between different computers, ensuring that Java code written on one machine can run smoothly on any other Java-compatible machine. By managing memory, enforcing security, and providing features like dynamic loading and JIT compilation, the JVM creates a robust and efficient environment for Java applications.