Programming Languages and OOP Concepts

Programming Languages

• Programming languages are categorized into imperative, procedural, and object-oriented types.
• Imperative languages use commands, where programmers specify inputs and the language returns an appropriate output.
• Procedural languages have a step-by-step approach with commands followed by results.
• Object-oriented languages group data and functions into objects, which can interact with other objects.
• Examples of languages include SQL (imperative), Fortran and Basic (procedural), Pascal and C++ (procedural), and Java and C# (object-oriented).

Object-Oriented Programming (OOP)

• OOP is a programming approach that organizes software design around data, or objects.
• Each object has data members (variables) and methods (functions).
• An important concept in OOP is encapsulation, where data and methods are bundled together.
• OOP improves software design, maintenance, and code reuse.
• Foundational OOP concepts include class, attributes (data members), method, inheritance to reuse code, polymorphism to create adaptable applications, and abstraction for simplified complexity.

Classes and Objects

• Classes are blueprints for creating objects.
• Objects are instances of classes.
• Classes define the structure and behavior of objects.
• Objects store data and use methods to perform operations.
• The concept of encapsulation is crucial for organizing and protecting data within a class. It means data is hidden internally and only accessible through methods.

Access Modifiers

• Access modifiers control how members (data & functions) of a class can be accessed from other parts of the program.
• public: members accessible from anywhere.
• private: members accessible only within the class.
• protected: members accessible within the class and subclasses.

Constructors

• Constructors are special methods automatically called when an object is created.
• They initialize the object's data members.
• Constructors often take parameters to control initialization values.

Inheritance

• Inheritance allows creating new classes (subclasses) based on existing classes (superclasses).
• Subclasses inherit attributes and methods from superclasses.
• This promotes code reuse and reduces redundancy.

Java

• Java is an object-oriented programming language created by James Gosling, originally named Oak.
• Java is platform-independent, meaning code can run on different operating systems.
• Java uses a compiler to translate Java source code into bytecode.
• bytecode is then executed by the Java Virtual Machine (JVM). The JVM is platform-specific enabling Java code to run across different operating systems.
• Key features of Java include object-orientation, portability, security, and high performance.
• Java uses the main function as the entry point for any Java program.

Java Data Types

• Java has various data types for storing different kinds of data.
• Primitive types are built-in (e.g., int, float, boolean) while non-primitive types are user-defined types (e.g. objects).
• Java uses a class hierarchy for data types similar to its object-oriented structure.

Java Variables

• Java variables store data values.
• Variables can be local (inside a method), instance (part of an object), or static (associated with a class, rather than an object).
• There are specific naming conventions related to variable types (local, instance etc) impacting their use.

Java Operators

• Java operators perform calculations and operations.
• There are different categories like arithmetic, relational, logical, and assignment operators with specific precedence rules.
• These operators can perform various operations including comparisons, arithmetic, and logical calculations on data.

Java Examples

• Various examples demonstrate how to use Java operators and data types in code.