Java Programming Essentials

Essentials of Java Programming

• Lesson 1 covers the essentials of Java Programming.

Agenda

• The first lesson discusses the Program Development Life Cycle.
• It covers the basics of Java.
• The anatomy of a Java program is presented.

Program Development Life Cycle (PDLC)

• PDLC is a process used by software developers to create software programs.
• PDLC includes stages from the initial idea to the final release and maintenance.
• The objective of the PDLC is to create software that is reliable and meets desired objectives.
• PDLC stages include planning, analysis, design, development, testing, deployment, and maintenance.
• Each stage has its own set of activities, goals, and deliverables.
• PDLC aims to create high-quality software programs that meet users' needs.

Phases of PDLC

• Phases are conceptualization, design, implementation, testing, deployment, and maintenance.

Conceptualization Phase

• Software requirements are gathered and analyzed.
• The team defines the project scope, timeline, and budget.
• A project plan outlining objectives, timelines, deliverables, and resources is developed.

Design Phase

• The team creates the software design based on requirements gathered during planning.
• Software architecture, data models, and employed algorithms are designed.
• Prototyping helps visualize appearance and functionality.

Implementation Phase

• The team writes code for the software.
• Programming languages and tools are used to create software as per design specifications.
• Unit testing ensures each software component functions as intended.

Testing Phase

• The team tests the entire software using various techniques to identify and fix bugs or defects.
• Functional testing confirms that the software meets requirements outlined in the planning stage.
• Performance testing, security testing, and other types of testing are performed.

Deployment Phase

• Software releases to end-users.
• Software is installed on appropriate hardware and configured for use.
• Documentation and training is given to users.
• Ongoing maintenance and support are available.

Maintenance Phase

• Involves ongoing support and upkeep of the software.
• Fixes any bugs or defects that emerge after deployment.
• Updating software for new requirements.
• Technical support helps for all users.
• Maintenance can continue for the life of the software, matching user and organizational needs.

Java

• Java is a programming language for developing software applications.
• Java can be run on various operating systems without code modification.
• Java code is compiled into bytecode, executable on any machine with a Java Virtual Machine (JVM).
• The JVM transforms bytecode into machine code for the processor to execute.

History of Java

• Introduced in 1995 by Sun Microsystems.
• Created by James Gosling, Mike Sheridan, and Patrick Naughton.
• Created to make a program that runs in multiple platforms.
• Key feature is "Write once, run anywhere"
• Oracle is the current owner.

Uses of Java

Web Applications

• Java is widely used for developing web applications on both the server and client sides.
• Popular web frameworks like Spring, Struts, and Hibernate are built using Java.

Mobile Applications

• Java is the main language for developing Android applications.
• Android Studio is the official IDE for Android app development and is built on top of Java.

Enterprise Applications

• Java is widely used for developing large-scale enterprise applications.
• Java's scalability and ability to handle large volumes of data make it ideal for finance, healthcare, and other industries.

Desktop Applications

• Java can develop desktop applications.
• It provides powerful user interface (UI) toolkits allowing the creation of rich and interactive applications.

Gaming

• Java gaming provides rich set of APIs for graphics, audio, and input.
• It is an ideal choice for game developers.

Internet of Things (IoT)

• Java offers key use in the development of IoT applications.
• Ability to run on low-power devices and support for sensors make it ideal for IoT projects.

Machine Learning and Artificial Intelligence

• Java's support for libraries such as Weka and Mahout makes it an ideal choice for AI applications.
• It can run on large-scale distributed systems for machine learning and AI applications.

How Java Works

• Programmers write Java Code
• Java compiler translates java code into bytecode
• A bytecode is a .class file that is in machine language format (1's and 0's)
• The .class file is then loaded into the JVM
• The .class file is verified to check for errors and security rule violations
• Bytecode is interpreted and executes instructions written in it
• Unused codes are removed in memory during garbage collection
• Finally, the program is terminated

Java's Programming Paradigm

Procedural

• Procedural is a programming paradigm.
• Involves writing a sequence of procedures or functions perform specific tasks.
• Procedures are useful rather than focusing on objects or data structures.

Object-Oriented

• Object-Oriented is a programming paradigm
• Organizes code into objects with properties (data) and methods (behavior)
• Characteristics: Inheritance, encapsulation, polymorphism, abstraction.

Parts of a Java Program

Access Modifier

• Restricts access to variables, methods, or classes.
• Includes four types: public, private, protected, and default.
• Public is most permissive.
• Private is most restrictive.
• Classes may only use public and default access modifiers.
• No access modifier specified means "default"

Class

• Represents built-in or custom building blocks in Java.
• Built-in Classes : standard classes or library classes - pre-defined classes that come with the Java programming language.
• Custom Class – Custom classes represent specific concepts, objects, or functionalities needed in projects.

Class Header

• Specifies class name.
• Every Java program must have at least one class definition.
• The Class serves as a container for program statements.
• You cannot have more than one public class in a single .java file.
• Program file names should match the public class name within Java projects.

Method Header

• The Method definition directly under the class.

Static vs Non-Static

• These are the types of methods that are available.
• Static Method is associated directly with the class itself
• Static Method is called directly without creating a class object.
• Non-Static Method is called Instance Method.
• Non-Static/Instance Method needs a class object to access.

Data Types

• Datatypes return a value when the method is done executing.
• The main method often uses "void", signaling no need to return a value.

Method Name

• The main method must be always named "main"
• The method name is where the program always starts.

Java Arrays

• String[] args means an array of type java.
• A string class accepts zero or multiple arguments.

Braces

• Braces {} that indicates the content of the class or method.

Method definition

• The method also means definition.
• A method serves as code that performs a specific task when executed.

Escape Sequences

• Consist of a backslash () followed by a letter or digit combination.
• Used in character strings for representing newlines, quotation marks, or other constants.
• Represents a single character, and is valid in character constants.

Basics of Java Programming Language

• Sample of Simple Addition Program:
• Code provided makes a simple addition using standard input

Import

• "import" includes classes or packages from other files/libraries.
• Importing lets you members without fully qualifying the name each time its referenced.

Package

• Organizes related classes and interfaces into a single namespace.
• A package is essentially a folder or directory that contains a set of related Java classes and interfaces.

Class

• A class is an instance that refers to a Java built-in type.
• A class provides a way to read input from various sources.

Instantiation

• Class instantiation creates an object from a class blueprint in Java.
• One only requires one scanner class and scanner variable per class.
• Format: Classname variable = new Classname;
• For Scanner Class:Scanner variable = new Scanner(System.in);

Method of Scanner Class

• Method reads the next integer value from the input source.
• Format for reading the next input from the console: Scannervariable.nextDatatype();
• Allowed data types to be read: nextBoolean, nextByte, nextDouble, nextFloat, nextInt, nextLine, nextLong, nextShort.

Concatenation

• Combines two or more strings into a single string.
• The '+' operator is also known as the concatenation operator.