java decorator pattern

Grotesque Gibbon answered on October 21, 2022 Popularity 10/10 Helpfulness 3/10

answer java decorator pattern

related Java Decorator design pattern example of implementation

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java decorator pattern

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// Java Decorator pattern

public interface WebPage { // Component interface
	public void display();
}

public class BasicWebPage implements WebPage{ // Base Concrete Component
	public void display() {
		System.out.println("renders HTML to stylesheet, run scripts");
	}
}

public abstract class WebPageDecorator implements WebPage{
	// one instance of WebPage, allow stacking
	protected WebPage webpage;
	
	// constructor allow different subtypes of WebPage to
	// be linked together in a stack
	public WebPageDecorator (WebPage webpage) {
		this.webpage = webpage;
	}
	
	public void display() {this.webpage.display();}
}

public class AuthorizedWebPage extends WebPageDecorator{ // Concrete Decorator

	// constructor uses abstract superclass's constructor
	// allows decorators to be stacked together
	public AuthorizedWebPage(WebPage decoratedPage) {
		super(decoratedPage);
	}
	
	// each decorator has its own responsibility
	public void authorizedUser() {System.out.println("Authorizing user");}
	
	public void display() {
		// to resursively call the display() behavior
		// concrete decorators invoke superclass's display() method
		// call to super.display() will cause the next WebPage in the 
		// stack to execute its version until get to BasicWebPage, 
		// where recursion will end b/c BasicWebPage is a concrete component
		// which does not aggregate other types of WebPage
		super.display();
		this.authorizedUser();
	}
}

//Concrete Decorator
public class AuthenticatedWebPage extends WebPageDecorator{ 

	public AuthenticatedWebPage(WebPage decoratedPage) {
		super(decoratedPage);
	}
	
	public void authenticateUser() {
		System.out.println("Authenticating user");
	}
	
	public void display() {
		super.display();
		this.authenticateUser();
	}
}

public class Program {
	public static void main(String[] args) {
		// stacking objects into an aggregate
		// the order you build the stack matters ()
		WebPage myPage = new BasicWebPage();
		myPage = new AuthorizedWebPage(myPage);
		myPage = new AuthenticatedWebPage(myPage);
		// recursively invoke aggregation stack to combine behavior
		myPage.display();
	}
}

// renders HTML to stylesheet, run scripts
// Authorizing user
// Authenticating user

Popularity 10/10 Helpfulness 3/10 Language java

Source: Grepper

Tags: decorator java

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Contributed on Oct 21 2022

Grotesque Gibbon

0 Answers Avg Quality 2/10

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Java Decorator design pattern example of implementation

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// The 'component' abstract class
public abstract class Beverage
{
	String description = "Unknown Beverage"

	public String getDescription()
	{
		return description;
	}

	public abstract double cost();
	// Other useful methods here

}

// The 'ConcreteComponent' classes
public class HouseBlend extends Beverage
{
	public HouseBlend()
	{
		description = "House Blend Coffee";
	}

	public cost double()
	{
		return 0.80;
	}
}

class DarkRoast extends Beverage 
{
	public DarkRoast()
	{
		description = "Dark Roast Coffee";
	}

	public double cost()
	{
		return 0.90;
	}
}


class Espresso extends Beverage
{
	public Espresso()
	{
		description = "Espresso";
	}

	public double cost()
	{
		return 1.99;
	}
}

class Decaf extends Beverage
{
	public Decaf()
	{
		description = "Decaf Coffee";
	}

	public double cost()
	{
		return 1.05;
	}
}

// The 'Decorator' abstract class
abstract class CondimentDecorator extends Beverage
{
	public abstract String getDescription();
}

// The 'ConcreteDecorator' classes
class Milk extends CondimentDecorator
{
	Beverage beverage;

	public Milk(Beverage beverage)
	{
		this.beverage = beverage;
	}

	public String getDescription()
	{
		return beverage.getDescription() + ", Milk";
	}

	public double cost()
	{
		return beverage.cost() + 10; // Assuming milk adds 0.10 to the cost
	}
}

Popularity 8/10 Helpfulness 1/10 Language java

Source: Grepper

Tags: decorator deco

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Contributed on Nov 10 2023

Depressed Donkey

0 Answers Avg Quality 2/10

java decorator design pattern

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// Interface for the component that will be decorated
interface Component {
    void operation();
}

// Concrete implementation of the component
class ConcreteComponent implements Component {
    @Override
    public void operation() {
        System.out.println("ConcreteComponent operation");
    }
}

// Abstract decorator class
abstract class Decorator implements Component {
    protected Component component;

    public Decorator(Component component) {
        this.component = component;
    }

    @Override
    public void operation() {
        component.operation();
    }
}

// Concrete decorator class adding extra functionality
class ConcreteDecorator extends Decorator {
    public ConcreteDecorator(Component component) {
        super(component);
    }

    @Override
    public void operation() {
        super.operation();
        addExtraFunctionality();
    }

    private void addExtraFunctionality() {
        System.out.println("Added extra functionality");
    }
}

public class Main {
    public static void main(String[] args) {
        // Creating a concrete component
        Component component = new ConcreteComponent();

        // Decorating the component with extra functionality
        Component decoratedComponent = new ConcreteDecorator(component);

        // Calling the operation on the decorated component
        decoratedComponent.operation();
    }
}

Popularity 7/10 Helpfulness 1/10 Language java

Source: chat.openai.com

Tags: decorator java

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Contributed on Mar 22 2024

Nitish Kumar

0 Answers Avg Quality 2/10

java decorator pattern

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