Java Fundamentals: OOP Principles, Collections, IO Streams, Socket Programming, Databases, and JSP Overview

This article begins with a motivational preface for programmers and then dives into core Java fundamentals.

1. Object‑Oriented Programming three main features : inheritance, encapsulation, and polymorphism are explained with practical notes such as single inheritance for classes, multiple inheritance for interfaces, and how encapsulation is realized through JavaBeans.

2. Java Collections Framework is illustrated with a diagram and descriptions of the key interfaces: Collection (parent of List, Set, Queue), Map (key‑value storage, e.g., HashMap), List (ordered, repeatable, e.g., ArrayList), Comparator and Comparable for sorting.

3. Java I/O Streams

• Byte streams: example code shows reading and writing bytes with FileInputStream and FileOutputStream and the importance of closing streams.

• Buffered byte streams: BufferedInputStream and BufferedOutputStream improve efficiency.

• Character streams: InputStreamReader / OutputStreamWriter with encoding, and convenience classes FileReader / FileWriter.

• Buffered character streams: BufferedReader and PrintWriter.

• Serialization: ObjectOutputStream and ObjectInputStream for persisting objects, with the file path stored in a String.

4. Socket Communication (multithreaded) outlines the typical steps: server socket creation and listening, client socket connection, spawning a new thread on the server to handle each client, and the exchange of request and response streams.

5. Relational Database Basics

• Three normal forms are listed.

• T‑SQL overview with a diagram.

• Common DML statements are provided: INSERT, DELETE, TRUNCATE, UPDATE, and a sub‑query example.

6. Web Development Section

• A brief JavaScript summary (link provided).

• JSP fundamentals: how a JSP page is compiled into a servlet, the lifecycle methods jspInit and jspService, and the nine implicit objects (e.g., request, response, session, application).

• Common JSP methods such as request.setCharacterEncoding, request.setAttribute, request.getRequestDispatcher(...).forward, and response.setContentType, response.sendRedirect.

• Differences between request forwarding (server‑side, same URL) and redirecting (client‑side, new request, URL changes).

• Session lifecycle and the need for session passivation (serialization to disk) when many users are present.

• Application scope object sharing across users.

• JSP directives ( page, include, taglib) and actions ( jsp:forward, jsp:param, jsp:include, jsp:plugin, jsp:useBean, jsp:setProperty, jsp:getProperty).

• Web listeners for HttpSession, ServletContext, and ServletRequest events, with diagrams of their classifications.

• MVC models: Model‑1 (JSP + JavaBean) and Model‑2 (Servlet controller, JSP view), describing request flow from JSP to servlet, service layer, DAO, and back to JSP.

Overall, the article serves as a concise reference for Java developers preparing for interviews or seeking a solid foundation in core Java, web technologies, and related server‑side concepts.