Essential Java Programming Concepts and Definitions

Posted on Mar 5, 2026 in Computers

Unit I: Core Java Fundamentals

  • OOP: A programming style that organizes software using objects containing data and methods.
  • Encapsulation: Binding data and methods together while restricting direct access.
  • Abstraction: Hiding complex details and showing only essential functionality.
  • Inheritance: A mechanism where one class acquires properties and methods of another.
  • Class & Object: A class is a blueprint defining properties and behaviors; an object is its runtime instance.
  • Java Introduction: A platform-independent, secure, object-oriented programming language.
  • Structure of Java Program: Consists of class definitions containing the main() method.
  • Compilation & Running: Java is compiled with javac and executed with the java interpreter.
  • Constants/Literals: Fixed values like numbers, characters, and strings used in programs.
  • Keywords: Reserved words in Java that have special meaning and cannot be used as identifiers.
  • Variables/Identifiers: Named storage locations used to store data in programs.
  • Data Types: Define the type and size of data, including primitive and non-primitive types.

Object-Oriented Programming and Advanced Java

  • Class Variables: Variables declared static and shared among all objects of a class.
  • Variable Scope: Local, class, and instance variables classified based on scope and lifetime.
  • Constructors: Special methods used to initialize objects at creation time (default and parameterized).
  • Visibility Labels: Access modifiers controlling accessibility: public, private, protected.
  • Inheritance/Superclass: Superclass provides features that subclass extends and reuses.
  • Final Method: A method that cannot be overridden by subclasses.
  • Static Method: Method belonging to a class and callable without creating objects.
  • Abstract Class: A class with abstract methods used to define common structure for subclasses.
  • Aggregation/Composition: “Has-a” relationships, with composition being stronger and dependent.
  • Messaging: Communication between objects through method calls.
  • Multithreading: Running multiple threads concurrently to improve performance.
  • Thread Class/Interface: Two ways to create threads: extending Thread or implementing Runnable.
  • Thread Priority: Determines scheduling preference of threads.
  • Synchronization: Mechanism to avoid conflicts when multiple threads access shared data.
  • Deadlock: Situation where threads wait forever due to circular resource dependency.
  • Packages: Organized groups of classes and interfaces for modular programming.
  • Interfaces: Completely abstract types defining methods a class must implement.
  • Instanceof Operator: Checks if an object belongs to a particular class or interface.
  • Dynamic Method Dispatch: Runtime polymorphism deciding which method version to execute.

Exception Handling, I/O, and Networking

  • Exception Handling: Technique to detect, handle, and recover from runtime errors gracefully.
  • Types of Exceptions: Includes checked, unchecked, and errors in Java.
  • Try-Catch Block: Used to catch and handle exceptions without crashing the program.
  • Multiple Catch: Allows handling different exception types separately.
  • Custom Exceptions: User-defined exceptions created for specific error situations.
  • File I/O: Reading and writing data using files and streams.
  • Character/Byte Streams: Classes for handling text and binary data flow respectively.
  • Serialization: Converting an object into a byte stream for storage or transmission.
  • Networking Basics: Java supports internet communication using socket programming.
  • TCP/IP Client Socket: Client-side connection for sending/receiving data.
  • URL & URLConnection: Classes to access internet resources and communicate with web servers.
  • Datagram/UDP: Connectionless packet-based communication for fast data transfer.

Applets and GUI Development

  • Applet Basics: Small Java programs that run inside a browser or applet viewer.
  • Applet Architecture: Based on predefined methods controlling its lifecycle and behavior.
  • Applet Lifecycle: init(), start(), stop(), destroy() methods executed by the browser.
  • Parameter Passing: Sending values from HTML to applet for customized behavior.
  • Applet Graphics: Drawing shapes like lines, ovals, rectangles using the Graphics class.
  • AWT Components: GUI elements like buttons, labels, and text fields.
  • Containers: Hold and manage GUI components in AWT.
  • Layout Managers: Automatically arrange GUI components inside containers.
  • Listeners/Adapters: Used to handle user events with simplified adapter classes.
  • Swing Intro: Lightweight, flexible GUI toolkit providing advanced components.