Let’s embark on a journey to discover the most important parts of Java 21 . I’ll cover the essentials, highlight new features in Java 21, and provide code samples and explanations. At the end of this article you’ll get a solid foundation and pointers for deeper study. Let's get started! Java 21: 1 Hour Crash Course 1. Introduction Java is a powerful, object-oriented programming language. Java 21, released in September 2023, brings performance improvements and new features. Prerequisites: Basic programming concepts (variables, loops, functions). Java installed (JDK 21). 2. Your First Program public class HelloWorld { public static void main ( String [ ] args ) { System . out . println ( "Hello, Java 21!" ) ; } } public class HelloWorld — Defines a class. public static void main — Entry point. System.out.println — Prints to console. 3. Variables and Data Types int age = 25 ; double price = 19.99 ; boolean isJavaFun = true ...