Understanding Requirement: Why Java
Why Java is important to the Internet
Java On Linux
First Java Program
Java Virtual Machine Architecture
Class Loading Process by Class Loaders
Role Of Just In Time Compiler
Execution Engine
Data Types
Variables
Arrays
Operators
Arithmetic Operations
Shifting Operators
Logical Operators
Control Statements
Object Oriented Paradigms
The Three OOP principles
Looping Statements
JAVA Class Fundamentals
Command Line Arguments
Static Initialize
Creating an Object
Instance Variable Hiding
Overriding and Overloading of methods
Understanding The Access Controls
Nested And Inner Classes
Dynamic Method Dispatching
Abstract Classes
Using Final To Prevent Overriding & Inheritance
Garbage Collection
Defining a package
Understanding Classpath
Access Protection
Importing packages
Defining and Implementing An Interface
Abstract classes vs Interfaces
Generics
Annotations
Varargs
Foreach
Fundamentals Of Exception Handling
Types Of Exceptions
Learning exception handling, try-catch, multiple catch clauses
Nested Try Statements
Throw, Throws and Finally
Custom Exceptions
Java Thread Model
Creating A Thread
Context Switching
Synchronization: Methods And Statements
Inter-thread Communication
Before starting speaking about any specific architecture, let me mention types of architecture. These are: Single Tier Architecture, Two Tier Architecture, Three Tier Architecture and generally N- Tier Architecture. The word “tier” is interchangeable with “layer”.
Usually, applications have the following layers: Presentation Layer, Business Layer and Data Layer. Let’s revisit each of the layers in detail:
Presentation layer is the top most tier of architecture and it is also known as Client Layer. This is the layer we see during using a software. On this layer we can access the webpages. This layer is used to communicate with Application layer. User actions like: mouse click, keyboard type or etc. are passed from presentation layer to Application Layer. For example, login page of any website where an end user could see text boxes and buttons to enter credentials (username and password) and then sign-in. To say it shortly, it is to view the application.
Application Layer is also known as Business Layer is the tier which holds the actual business logic of our application. To continue the previous example of log-in webpage Application layer interacts with Database layer and sends required information to the Presentation layer. This layer is a mediator between Database and Presentation layers. Complete business logic will be written in this layer.
Data Layer is the place where we store the information, data. Application layer is the one which is communicating with Database layer in order to retrieve data. It contains methods for connecting database and then performs required operations e.g.: insert, update, delete etc.
Single Tier Architecture
One tier architecture is the most primitive one and the least used in real applications as in this case we have all layers: Presentation, Application and Data in the same package. In that case, data layer is inside the application and it stored data in local system or shared drive. But MS office system is an example of one tier architecture.
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