Java Object-oriented Programming & Exception Handling

Java: Object-oriented Programming

• Core Concepts:
  • Classes and Objects:
    • Class: Blueprint for creating objects (contains fields and methods).
    • Object: Instance of a class.
  • Encapsulation:
    • Bundling data (attributes) and methods (functions) together.
    • Access modifiers: private, public, protected, and default.
  • Inheritance:
    • Mechanism where one class inherits properties and methods from another.
    • Enables code reusability.
  • Polymorphism:
    • Ability to perform a single action in different ways.
    • Achieved through method overloading (same method name, different parameters) and method overriding (subclass provides a specific implementation).
  • Abstraction:
    • Hiding complex implementation details and showing only essential features.
    • Achieved using abstract classes and interfaces.

Java: Exception Handling

• Definition:

  • Mechanism to handle runtime errors, ensuring the normal flow of execution.

• Key Components:

  • Exception: An event that disrupts the normal execution of a program.
  • Error: Issues that cannot be handled by the program (e.g., OutOfMemoryError).

• Exception Handling Keywords:

  • try: Block of code that may throw an exception.
  • catch: Block that handles exceptions thrown by the try block.
  • finally: Block that executes code after try/catch, regardless of whether an exception occurred.
  • throw: Used to explicitly throw an exception.
  • throws: Declaration in a method signature that indicates a method might throw exceptions.

• Common Exceptions:

  • Checked Exceptions: Must be declared or caught (e.g., IOException).
  • Unchecked Exceptions: Do not need to be declared (e.g., NullPointerException, ArrayIndexOutOfBoundsException).

• Best Practices:

  • Catch specific exceptions rather than generic ones.
  • Clean up resources in the finally block.
  • Use custom exceptions for better error handling in application-specific scenarios.

Java: Object-oriented Programming

• Classes and Objects:

  • A class serves as a blueprint for object creation, encompassing fields (attributes) and methods (functions).
  • An object is a concrete instance derived from a class.

• Encapsulation:

  • Combines data (attributes) and methods into a single unit.
  • Access modifiers control visibility:
    • private: Accessible only within the class.
    • public: Accessible from anywhere.
    • protected: Accessible within the class and subclasses.
    • Default: Accessible within the same package.

• Inheritance:

  • Allows one class to inherit properties and methods from another class.
  • Promotes code reusability and establishes a relationship between classes.

• Polymorphism:

  • Enables a single action to take different forms.
  • Method overloading allows using the same method name with different parameters.
  • Method overriding allows a subclass to provide a specific implementation of a method from its superclass.

• Abstraction:

  • Conceals complex implementation details, exposing only the essential features.
  • Implemented through abstract classes (cannot be instantiated) and interfaces (define methods that must be implemented).

Java: Exception Handling

• Definition:

  • A mechanism designed to manage runtime errors, ensuring that the normal flow of execution is maintained.

• Key Components:

  • Exception: An event that interrupts normal program execution.
  • Error: Serious issues that are typically not recoverable by the application, such as OutOfMemoryError.

• Exception Handling Keywords:

  • try: Code block that may throw an exception.
  • catch: Block that catches and handles exceptions thrown by the try block.
  • finally: Block that executes after try/catch, regardless of whether an exception was thrown.
  • throw: Used to explicitly trigger an exception.
  • throws: Indicates in the method signature that a method may throw exceptions.

• Common Exceptions:

  • Checked Exceptions: Must be declared or caught in the code (e.g., IOException).
  • Unchecked Exceptions: Do not require declaration (e.g., NullPointerException, ArrayIndexOutOfBoundsException).

• Best Practices:

  • Focus on catching specific exceptions to improve handling.
  • Utilize the finally block to clean up resources.
  • Implement custom exceptions for more effective error handling tailored to application-specific scenarios.