Object-Oriented Programming (OOP) Fundamentals

Object-Oriented Programming (OOP)

• Key Concepts:
  • Classes and Objects
  • Inheritance
  • Polymorphism
  • Encapsulation
  • Abstraction
• Class and Object:
  • A class is a blueprint or template for creating objects.
  • An object is an instance of a class, having its own state and behavior.
• Inheritance:
  • A child class inherits properties and behavior from a parent class.
  • Child class can also override or extend the parent class's behavior.
• Polymorphism:
  • Method Overloading: multiple methods with same name but different parameters.
  • Method Overriding: a child class provides a different implementation of a method already defined in its parent class.
• Encapsulation:
  • Hiding internal implementation details of an object from the outside world.
  • Data Hiding and Abstraction.
• Abstraction:
  • Showing only necessary information to the outside world while hiding internal details.

Multithreading

• Key Concepts:
  • Thread: a separate flow of execution.
  • Process: a program in execution.
  • Multithreading: multiple threads within a process.
• Thread Creation:
  • Extending Thread class or implementing Runnable interface.
  • start() method to begin thread execution.
• Thread Synchronization:
  • synchronized keyword to ensure only one thread accesses a resource at a time.
  • wait() and notify() methods for thread communication.
• Thread Safety:
  • Ensuring that multiple threads do not interfere with each other's execution.

Data Structures

• Array:
  • A fixed-size, homogeneous collection of elements.
  • Elements are accessed using an index.
• ArrayList:
  • A dynamic-size, homogeneous collection of elements.
  • Elements are accessed using an index.
• LinkedList:
  • A dynamic-size, homogeneous collection of elements.
  • Elements are accessed using a reference to the next node.
• Stack and Queue:
  • Last-In-First-Out (LIFO) and First-In-First-Out (FIFO) data structures.
  • Implemented using arrays or linked lists.

Java Syntax

• Variables:
  • Declared using type variableName syntax.
  • Primitive types (e.g., int, double) and reference types (e.g., String).
• Operators:
  • Arithmetic operators (e.g., +, -, *, /)
  • Comparison operators (e.g., ==, !=, >, <)
  • Logical operators (e.g., &&, ||, !)
• Control Structures:
  • Conditional statements (e.g., if, if-else)
  • Loops (e.g., for, while, do-while)
  • Switch statements

Exception Handling

• Try-Catch Block:
  • try block contains code that may throw an exception.
  • catch block handles the exception.
• Types of Exceptions:
  • Checked Exceptions: compiler checks for exceptions at compile-time.
  • Unchecked Exceptions: compiler does not check for exceptions at compile-time.
• Throwing Exceptions:
  • throw keyword to throw an exception.
  • throws keyword to declare an exception in a method signature.
• Custom Exceptions:
  • Creating custom exception classes by extending Exception class.

Object-Oriented Programming (OOP)

• A class is a blueprint or template for creating objects, defining their properties and behavior.
• An object is an instance of a class, having its own state and behavior.
• Classes support inheritance, polymorphism, encapsulation, and abstraction.

Inheritance

• A child class inherits properties and behavior from a parent class.
• A child class can override or extend the parent class's behavior.

Polymorphism

• Method Overloading: multiple methods with the same name but different parameters.
• Method Overriding: a child class provides a different implementation of a method already defined in its parent class.

Encapsulation

• Hiding internal implementation details of an object from the outside world.
• Data Hiding and Abstraction are achieved through encapsulation.

Abstraction

• Showing only necessary information to the outside world while hiding internal details.

Multithreading

• A thread is a separate flow of execution.
• A process is a program in execution.
• Multithreading involves multiple threads within a process.

Thread Creation

• Threads can be created by extending the Thread class or implementing the Runnable interface.
• The start() method begins thread execution.

Thread Synchronization

• The synchronized keyword ensures only one thread accesses a resource at a time.
• wait() and notify() methods enable thread communication.

Thread Safety

• Ensuring that multiple threads do not interfere with each other's execution is crucial.

Data Structures

Array

• A fixed-size, homogeneous collection of elements.
• Elements are accessed using an index.

ArrayList

• A dynamic-size, homogeneous collection of elements.
• Elements are accessed using an index.

LinkedList

• A dynamic-size, homogeneous collection of elements.
• Elements are accessed using a reference to the next node.

Stack and Queue

• Last-In-First-Out (LIFO) and First-In-First-Out (FIFO) data structures.
• Implemented using arrays or linked lists.

Java Syntax

Variables

• Declared using type variableName syntax.
• Primitive types (e.g., int, double) and reference types (e.g., String) are supported.

Operators

• Arithmetic operators (e.g., +, -, *, /) are used for mathematical operations.
• Comparison operators (e.g., ==, !=, >, <) are used for conditional checks.