Design Patterns

Design patterns are standardized solutions to recurring design problems in object-oriented systems. They capture best practices and provide a common language for software developers to discuss and apply design principles.

Some commonly used design patterns include:

• Singleton Pattern: Ensures that a class has only one instance, and provides a global point of access to that instance.
• Factory Pattern: Provides an interface for creating objects, but allows subclasses to decide which class to instantiate.
• Adapter Pattern: Allows objects with incompatible interfaces to work together by creating a common interface that both objects can use.
• Decorator Pattern: Allows behavior to be added to an individual object dynamically, without affecting the behavior of other objects. It provides a flexible alternative to subclassing for extending functionality.

Design patterns are not specific to any programming language and can be applied to any object-oriented system. They can improve code reusability, readability, and maintainability.

Let's take a look at an example of the Decorator pattern in Java:

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}

// Decorator pattern example

​

interface Beverage {

    String getDescription();

    double getCost();

}

​

class Espresso implements Beverage {

    public String getDescription() {

        return "Espresso";

    }

    public double getCost() {

        return 1.99;

    }

}

​

class Milk implements Beverage {

    private Beverage beverage;

​

    public Milk(Beverage beverage) {

        this.beverage = beverage;

    }

​

    public String getDescription() {

        return beverage.getDescription() + ", Milk";

    }

​

    public double getCost() {

        return beverage.getCost() + 0.49;