Java Introduction

Java Introduction

• Java is a programming language focused on portability, simplicity, and security.
• Key features of Java include:
  • Simple: Easy to learn with clear syntax (based on C++). Supports dynamic compilation and garbage collection.
  • Object-Oriented: Encapsulates data and methods within objects. Supports inheritance and polymorphism.
  • Portable: Platform-independent, allowing code to run on different operating systems.
  • Secured: Employs security mechanisms such as bytecode verification and access control.
  • Robust: Provides exception handling and garbage collection for reliable coding.
  • Architecture Neutral: Compiles into platform-independent bytecode.
  • Interpreted: Uses JVM to execute bytecode, making it platform-independent.
  • High Performance: Achieves high performance through Just-in-Time (JIT) compilation.
  • Multithreaded: Allows multiple threads to execute concurrently, improving efficiency.
  • Distributed: Facilitates development of distributed applications using remote method invocation (RMI).

Java Hello World Program

• The "Hello World" program demonstrates basic Java syntax and execution.
• The program requires a class with a main method.
• The System.out.println() statement prints the output to the console.
• The program is compiled using the javac command and executed using the java command.

Java JVM, JRE and JDK

• Java Development Kit (JDK): A software development environment for creating Java applications and applets. Includes JRE, compiler, archiver, documentation generator, and other tools.
• Java Runtime Environment (JRE): Includes JVM, core classes, and supporting files for running Java applications.
• Java Virtual Machine (JVM): An interpreter responsible for executing Java bytecode line by line. Acts as a bridge between the compiled code and the underlying operating system.
• JRE Components:
  • Deployment technologies: Deployment, Java Web Start, Java Plug-in.
  • User interface toolkits: AWT, Swing, Java 2D, Accessibility, Image I/O, Print Service, Sound, DnD, input methods.
  • Integration libraries: IDL, JDBC, JNDI, RMI, RMI-IIOP, scripting.
  • Other base libraries: International support, I/O, extension mechanism, Beans, JMX, JNI, Math, Networking, Security, Serialization, XML JAXP.
  • Lang and util base libraries: Lang, util, management, versioning, zip, instrument, reflection, Collections, Concurrency Utilities, JAR, Logging, Preferences API, Ref Objects, Regular Expressions.
• Setting Path: Setting the path variable allows access to tools such as javac and java from any directory. This is crucial for running Java programs outside the JDK/bin folder.

Editions of Java

• Java Platform, Standard Edition (Java SE): Provides core Java language features, basic types and objects, high-level classes for networking, security, database access, GUI development, and XML parsing.
• Java Platform, Enterprise Edition (Java EE): Built upon Java SE, offers an API and runtime environment for developing and running enterprise-level applications, including multi-tiered, scalable, reliable, and secure network applications.
• Java Platform, Micro Edition (Java ME): Designed for resource-constrained devices like mobile phones, providing a subset of the Java SE API and specialized libraries for small device development.
• Java FX: A platform for creating rich internet applications using Java FX Script, a declarative language compiled to Java bytecode. Allows applications to interact with Java language classes.