How does Java work under the hood?

First of all, what is Java?

Java is a multi-platform object-oriented programming language.

"Multi-platform" means that it can not only be used to create web applications, mobile applications and games, but can also run on any device you can think of.

Object-oriented programming (OOP) means that its main concepts revolve around objects, which are just data with properties and behaviors.

Now, how does it work in our computer?

Java processing can be likened to a journey, and the best way to describe it is to break it down into steps:

Step 1: Code Script

As we all know, code needs to be written in the form of ".java" files in an editor (Notepad, IDE, etc.).

But this code can only be understood by humans, so we need a way to convert the Java code into something that a computer can read and understand.

Step 2: Compile into bytecode

Javac or Java compiler, as the name suggests, is the standard Java compiler.

What it does is, given certain commands, it takes Java code and compiles it into what's called bytecode.

Bytecode is a set of instructions that can run on any device as long as the device contains a Java Virtual Machine (JVM).

Step 3: The role of JVM

JVM (Java Virtual Machine) is a powerful translator that takes the bytecode and makes it understood by the computer processor, and is used by the JRE (Java Runtime Environment ) provides different libraries or interfaces to help the JVM run seamlessly.

But there is another point. The JVM will not run our bytecode directly. It will go through the following process: - Explanation: Our JVM converts each line of code into instructions or actions that the computer should perform, also known as bytecode. - JIT compilation: In order to improve running speed, JVM utilizes JIT (just-in-time compiler) to convert these bytecodes into native machine code (computer processor can understood language).

Step 4: Run the program

Now that the JVM has done its job, it finally sends instructions to the computer to run or print what the developer wants to print (e.g. "hello world!!" on the screen, or that cool game above? ).

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