Java Overview

Introduction to Java

• High-level multi-paradigm programming language
• Designed by James Gosling in 1990 at Sun Microsystems
• Gained popularity due to platform-independent bytecode

History

• First demonstration: Star 7 PDA
• Java mascot: Duke
• Currently one of the world's most popular programming languages

Applications

• Powers enterprise web apps with Spring Framework
• Used in big data pipelines with Hadoop
• Development of mobile apps on Android
• Controls NASA's Maestro Mars rover

Key Features

• Compiles to bytecode instead of machine code (unlike C/C++)
• Runs on any operating system via Java Virtual Machine (JVM)
• Compiled and interpreted language
• Requires Java Runtime Environment (JRE) for execution
• "Write once, run anywhere" capability

Language Characteristics

• Strongly typed language
• Curly brace syntax similar to C family
• High-level features include:
  • Garbage collection
  • Runtime type checking
  • Reflection

Getting Started with Java

1. Install Java Development Kit (JDK)
2. Create a file with a .java extension
   • File name should match the class name
   • Class must contain a main method (entry point of the program)

Basic Syntax

• Define a variable:
  • Start with a type, followed by a name and value
• Print to standard output using the built-in System class

Classes and Methods

• Define functions as methods within a class:
  • public: accessible outside the class
  • static: member of the class, not an instance
• Provide a return type, name, and return value
• Create custom classes (blueprints for objects)
  • Add attributes and methods
  • Use the new keyword to instantiate objects

Object-Oriented and Functional Support

• Java is object-oriented but supports functional programming patterns (e.g., lambda expressions)

Compiling and Running Java Programs

• Use the compiler to generate a .class file (contains bytecode)
• Run the bytecode with the java command via JVM

Conclusion

• Successfully built an enterprise-grade application
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