Day 1: Intro to Java Programming

Hello everyone
This is my Day 1 learning blog on Java programming. I am a beginner, and in this post, I will share what I learned in a simple and easy way.

1. What is Java?

• Java is a programming language and one of the most popular and widely used languages.
• Java is platform-independent, which means write once, run anywhere.
• Java is an object-oriented programming language.
• Java allows humans to write programs using English-like syntax, which computers can process.

2. How Do Humans and Machines Understand Code?

• Humans understand languages like English
• Machines understand only binary code (0's and 1's). For example: 10101010
• So, Java acts as a bridge between humans and machines using multiple components (JDK, JVM, etc.).

Java Works in Levels

=> Level 1: JDK (Java Development Kit)

JDK (Java Development Kit)

• It is used to write and develop Java programs
• Java programs compiled using JDK are platform-independent, but JDK itself is platform-specific.

Example Java file:

Sample.java

If there is a mistake in code, then we will encounter a syntax error.

To compile Java code:

javac Sample.java

If compilation is successful, a new Sample.class will be generated in the location where your Sample.java file is located.

=> Level 2: JRE, JVM, and JIT

JRE (Java Runtime Environment)

• JRE (Java Runtime Environment) provides the required environment to run Java programs.
• It includes JVM and core Java libraries.
• JRE is responsible for executing .class files safely on the system.

JVM (Java Virtual Machine)

• JVM (Java Virtual Machine) executes Java bytecode.
• Acts as a bridge between Java and the system
• It converts bytecode into machine-specific instructions.
• JVM makes Java platform-independent.

JIT (Just-In-Time Compiler)

• JIT (Just-In-Time Compiler) converts bytecode into native machine code at runtime.
• It improves performance by compiling frequently used code.
• Conversion happens while the program is running.