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Questions and Answers
The ______ pattern ensures only one instance of a class
Singleton
The ______ principle hides implementation details and shows only necessary information
Encapsulation
The ______ pattern defines a one-to-many dependency between objects
Observer
Java has ______ data types, including byte, short, int, long, float, double, char, and boolean
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Inheritance allows creating a new ______ based on an existing class
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The ______ pattern provides a way to create objects without specifying the exact class of object
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Access modifiers in Java include ______, private, protected, and default (package-private)
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In Java, ______ are special methods that initialize objects when created
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What is the primary goal of the Singleton pattern, and how is it achieved?
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How does the Factory pattern decouple object creation from specific classes?
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What is the main purpose of the Abstract Factory pattern, and how is it achieved?
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How does the Adapter pattern enable incompatible objects to work together?
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What is the primary advantage of separating an object's abstraction from its implementation using the Bridge pattern?
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What is the key benefit of using the Composite pattern to compose objects into tree structures?
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How does the Observer pattern enable loose coupling and scalability?
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What is the primary advantage of using the Strategy pattern to define a family of algorithms?
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Study Notes
Design Patterns
- Creational Patterns:
- Singleton Pattern: ensures only one instance of a class
- Factory Pattern: provides a way to create objects without specifying the exact class of object
- Abstract Factory Pattern: provides a way to create families of related objects
- Structural Patterns:
- Adapter Pattern: allows two incompatible objects to work together
- Bridge Pattern: separates an object's abstraction from its implementation
- Composite Pattern: allows clients to treat individual objects and compositions of objects uniformly
- Behavioral Patterns:
- Observer Pattern: defines a one-to-many dependency between objects
- Strategy Pattern: defines a family of algorithms, encapsulates each one, and makes them interchangeable
- Template Method Pattern: defines the skeleton of an algorithm, allowing subclasses to customize it
Object-oriented Programming (OOP)
- Principles:
- Encapsulation: hiding implementation details and showing only necessary information
- Abstraction: exposing only necessary information and hiding implementation details
- Inheritance: creating a new class based on an existing class
- Polymorphism: objects of different classes responding to the same method call
- Concepts:
- Classes and Objects: classes define objects, objects have attributes and methods
- Constructors: special methods that initialize objects when created
- Inheritance and Interfaces: single and multiple inheritance, abstract classes and interfaces
- Access Modifiers: public, private, protected, default (package-private)
Java Syntax
- Variables and Data Types:
- Primitive Data Types: byte, short, int, long, float, double, char, boolean
- Reference Data Types: class, interface, array
- Variable Declaration:
type variableName [= value];
- Operators:
- Arithmetic Operators:
+,-,*,/,%, etc. - Comparison Operators:
==,!=,>,<,>=,<= - Logical Operators:
&&,||,!
- Arithmetic Operators:
- Control Flow:
- Conditional Statements:
if,if-else,switch - Loops:
while,for,do-while - Jump Statements:
break,continue,return
- Conditional Statements:
- Methods:
- Method Declaration:
accessModifier returnType methodName(parameters) { body } - Method Overloading: multiple methods with same name but different parameters
- Method Overriding: subclass provides a specific implementation for a method already defined in its superclass
- Method Declaration:
Design Patterns
-
Creational Patterns: ensure objects are created in a specific way
- Singleton Pattern: guarantees a single instance of a class
- Factory Pattern: creates objects without specifying the exact class
- Abstract Factory Pattern: creates families of related objects
-
Structural Patterns: deal with the structure of classes and objects
- Adapter Pattern: makes incompatible objects work together
- Bridge Pattern: separates abstraction from implementation
- Composite Pattern: treats individual objects and compositions uniformly
-
Behavioral Patterns: define interactions between objects
- Observer Pattern: sets up a one-to-many dependency between objects
- Strategy Pattern: allows interchangeable algorithms
- Template Method Pattern: defines a customizable algorithm skeleton
Object-oriented Programming (OOP)
-
Principles:
- Encapsulation: hides implementation details, shows only necessary info
- Abstraction: exposes necessary info, hides implementation details
- Inheritance: creates a new class based on an existing class
- Polymorphism: objects of different classes respond to the same method call
-
Concepts:
- Classes and Objects: classes define objects, which have attributes and methods
- Constructors: special methods that initialize objects when created
- Inheritance and Interfaces: single and multiple inheritance, abstract classes, and interfaces
- Access Modifiers: public, private, protected, default (package-private)
Java Syntax
-
Variables and Data Types:
- Primitive Data Types: byte, short, int, long, float, double, char, boolean
- Reference Data Types: class, interface, array
-
Variable Declaration:
type variableName [= value];
-
Operators:
-
Arithmetic Operators:
+,-,*,/,%, etc. -
Comparison Operators:
==,!=,>,<, etc.
-
Arithmetic Operators:
Creational Design Patterns
- Singleton Pattern ensures a class has only one instance and provides a global point of access to that instance, featuring a private constructor and a public static method to retrieve the instance.
- Thread-safe implementations of Singleton Pattern include synchronized methods and double-checked locking.
- Factory Pattern provides a way to create objects without specifying the exact class of object that will be created, decoupling object creation from specific classes.
- Abstract Factory Pattern provides an interface for creating families of related or dependent objects without specifying their concrete classes, combining multiple factory patterns to return a family of related objects.
Structural Design Patterns
- Adapter Pattern converts the interface of a class into another interface that clients expect, enabling incompatible objects to work together, with object adapter and class adapter implementations.
- Bridge Pattern separates an object's abstraction from its implementation, allowing them to vary independently, and decoupling abstraction from implementation to enable runtime changes to either.
- Composite Pattern composes objects into tree structures to represent part-whole hierarchies, enabling the treatment of individual objects and compositions uniformly through recursive composition.
Behavioral Design Patterns
- Observer Pattern defines a one-to-many dependency between objects, allowing objects to notify each other of changes, and consists of subject, observer, and notification, enabling loose coupling and scalability.
- Strategy Pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable, enabling runtime algorithm changes through context, strategy, and concrete strategies.
- Template Method Pattern provides a way to allow subclasses to override specific steps of an algorithm without changing its structure, enabling customization and code reuse through abstract class, template method, and hooks.
Other Design Patterns
- MVC Pattern separates an application into three interconnected components: model (data and business logic), view (user interface), and controller (handles user input and updates model and view).
- Dependency Injection Pattern provides components with dependencies, rather than hardcoding them, enabling loose coupling and testability through inversion of control.
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Description
Explore various design patterns in software development, including creational, structural, and behavioral patterns. Learn about Singleton, Factory, Adapter, and more.
