Java Programming Basics

Java Basics

• Java is a programming language developed by Sun Microsystems and now owned by Oracle.
• It was acquired by Oracle in 2010.
• It is both compiled and interpreted.
• It is known for its portability across different platforms.
• Java is open-source, meaning its source code is freely available for use and modification.
• Java is high-level and object-oriented, designed for ease of use and organization around objects.
• Java's popularity stems from its ability to run on any device with a Java Virtual Machine (JVM).
• This allows Java applications to run on diverse platforms.
• Java is used by developers to build various types of software.

Strengths of Java

• Simple: Easy to learn and use.
• Syntax: Similar to C/C++, familiar to those with C or C++ experience.
• Development Support: Facilitates efficient software creation.
• Portable: Runs on any device with a JVM.
• Secure: Built-in security features protect against vulnerabilities.
• High Performance: Optimized for speed and efficiency.
• Robust: Effectively manages errors and exceptions to maintain stability.

The Java Environment

• Java source code compiles into bytecode.
• Bytecode is not directly executed by the machine.
• The Java Virtual Machine (JVM) understands bytecode.
• The JVM uses a Java interpreter to convert bytecode into platform-specific machine code.
• Each platform has its own JVM.

Java Development Kit (JDK)

• Provides a Java compiler.
• Provides a Java Virtual Machine (JVM).
• Provides a set of libraries for programming.

The Java Virtual Machine (JVM)

• Interprets bytecode generated during Java source code compilation.
• Translates bytecode into instructions the underlying machine can execute..
• Handles automatic memory management, including reclaiming unused object memory.

Structure of a Java Program

• Packages: Namespaces organizing classes and interfaces like packages for utility classes (e.g., java.util.*).
• Classes: Fundamental building blocks of Java programs, blueprints for objects. Every Java program has at least one class, and the name must match the corresponding file name.
• Methods: Functions or procedures inside a class, performing actions. The main method (public static void main(String[] args)) is where the program execution begins.

An Example of Program Structure

• Package Declaration: package com.example;
• Class Declaration: public class HelloWorld { ... }
• Main Method: public static void main(String[] args) { ... }
• Statement: System.out.println("Hello, World!");

Packages in Java

• Divided into built-in and user-defined packages.
• The package keyword indicates a user-defined package for a class.
• Otherwise, the import keyword is used.

Eclipse IDE

• Open-source Integrated Development Environment (IDE) used primarily for Java development.
• Supports other languages via plugins.
• Provides a comprehensive environment for coding, debugging, and testing Java applications.

Essential Features of Eclipse

• Code Editor: Syntax highlighting and code completion
• Debugging Tools: Breakpoints, Step Execution, and Variable Inspection
• Project Management: Workspace to organize projects and resources

Concepts in Java Development with Eclipse

• Project: A folder containing Java code, libraries, and resources for applications (e.g., a calculator).
• Package: Organizes classes, like folders, grouping related classes for an application (e.g., input and output classes in a calculator).
• Class: Defines an object's structure and behavior (e.g., a Calculator class with add, subtract, etc. methods).
• Object: Instance of a class; an instantiation of the Calculator class.
• Methods: Blocks of code inside a class defining an object's actions (e.g., add, subtract)

Steps to Create Your First Project in Eclipse

• Open Eclipse.
• Create a new Java Project.
• Name your project (e.g., "MyFirstProject")

Steps to Create Your First Java Class

• Inside the project open the src folder.
• Create a new Java class (e.g., "MyFirstClass").
• Include the main method (public static void main(String[] args))

Write and Test Your First Code

• In the main method, type System.out.println("Hello, World!");
• To run, click the green play button.

Primitive Data Types

• Java has eight primitive data types that are fundamental.
  • int, float, double, char, boolean, byte, short, long

Examples of Primitive Data Types

• Demonstrate how to declare variables of these types and assign values

The Keyword "Final"

• Used to declare constants, Preventing changes to a variable's value once initialized.

Arithmetic Operators

• Perform basic math operations (+, -, *, /)

Relational Operators

• Compare values and return boolean results (==, !=, >, <, >=, <=)

Logical Operators

• Combine boolean expressions (&&, ||, !)

Assignment Operators

• = (simple assignment), +=, -=, *=

Increment and Decrement Operators

• Increment (++) and decrement (--) operators.

Conditional Statements

• if statements: Execute code based on true/false conditions

• else if Statements: Allows more than one condition to be checked.

• switch statements: Choose code based on different cases

Looping Structures

• for loops: Repeat code a set number of times.
• while loops: Repeat code as long as a condition is true.
• do-while loops: Similar to while but execute the code at least once.

Break and Continue Statements

• break: Terminates a loop.
• continue: Skips the current iteration of a loop.

Arrays

• A collection of values of the same type.
  • Single dimensional (arrays).
  • Multi dimensional (matrix).

Using Scanner Class

• Used to read input from the user (e.g., integers, strings).

Methods

• Blocks of code in classes, performing specific tasks and can optionally return a value.

• Modifiers: Define the access level of the method. Examples: public, private and protected

• Return Type: Indicates the type of value returned by the method.

• Method Name: Identifies the method uniquely.

• Parameters: Optional inputs to the method.

Method (2)

• Examples of method declarations and implementations showcasing Modifiers, Return Type, Method Name and Method Body.

Modifier

• Defines the accessibility level of classes, methods, and attributes. Example Modifiers include public, private, and protected.