tiennm99/java-design-patterns
1
0
Fork 0
mirror of https://github.com/tiennm99/java-design-patterns.git synced 2026-05-14 12:58:37 +00:00
Code Issues Packages Projects Releases Wiki Activity

docs: update decorator

Browse Source
This commit is contained in:
Ilkka Seppälä
2024-05-25 11:41:51 +03:00
parent b855476315
commit 410c0c69a3
1 changed files with 39 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files
decorator/README.md
+39 -38
View File
@@ -3,9 +3,10 @@ title: Decorator
category: Structural
language: en
tag:
- Gang of Four
- Enhancement
- Extensibility
- Gang of Four
- Object composition
- Wrapping
---
@@ -22,7 +23,7 @@ The Decorator pattern allows for the dynamic addition of responsibilities to obj
Real-world example
> There is an angry troll living in the nearby hills. Usually, it goes bare-handed, but sometimes it has a weapon. To arm the troll it's not necessary to create a new troll but to decorate it dynamically with a suitable weapon.
> Imagine a coffee shop where you can customize your coffee order. You start with a basic coffee, and you can add different ingredients like milk, sugar, whipped cream, and so on. Each addition is like a decorator in the Decorator design pattern. The base coffee object can be decorated with additional functionality (flavors, toppings) dynamically. For example, you can start with a plain coffee object, then wrap it with a milk decorator, followed by a sugar decorator, and finally a whipped cream decorator. Each decorator adds new features or modifies the behavior of the coffee object, similar to how the Decorator pattern works in software design.
In plain words
@@ -34,7 +35,9 @@ Wikipedia says
**Programmatic Example**
Let's take the troll example. First of all we have a `SimpleTroll` implementing the `Troll` interface:
There is an angry troll living in the nearby hills. Usually, it goes bare-handed, but sometimes it has a weapon. To arm the troll it's not necessary to create a new troll but to decorate it dynamically with a suitable weapon.
First, we have a `SimpleTroll` implementing the `Troll` interface:
```java
public interface Troll {
@@ -68,16 +71,12 @@ public class SimpleTroll implements Troll {
Next, we want to add a club for the troll. We can do it dynamically by using a decorator:
```java
@Slf4j
@RequiredArgsConstructor
public class ClubbedTroll implements Troll {
private final Troll decorated;
public ClubbedTroll(Troll decorated) {
this.decorated = decorated;
}
@Override
public void attack() {
decorated.attack();
@@ -99,39 +98,42 @@ public class ClubbedTroll implements Troll {
Here's the troll in action:
```java
// simple troll
LOGGER.info("A simple looking troll approaches.");
var troll=new SimpleTroll();
troll.attack();
troll.fleeBattle();
LOGGER.info("Simple troll power: {}.\n",troll.getAttackPower());
public static void main(String[] args) {
// change the behavior of the simple troll by adding a decorator
LOGGER.info("A troll with huge club surprises you.");
var clubbedTroll=new ClubbedTroll(troll);
clubbedTroll.attack();
clubbedTroll.fleeBattle();
LOGGER.info("Clubbed troll power: {}.\n",clubbedTroll.getAttackPower());
// simple troll
LOGGER.info("A simple looking troll approaches.");
var troll = new SimpleTroll();
troll.attack();
troll.fleeBattle();
LOGGER.info("Simple troll power: {}.\n", troll.getAttackPower());
// change the behavior of the simple troll by adding a decorator
LOGGER.info("A troll with huge club surprises you.");
var clubbedTroll = new ClubbedTroll(troll);
clubbedTroll.attack();
clubbedTroll.fleeBattle();
LOGGER.info("Clubbed troll power: {}.\n", clubbedTroll.getAttackPower());
}
```
Program output:
```java
A simple looking troll approaches.
The troll tries to grab you!
The troll shrieks in horror and runs away!
Simple troll power:10.
```
11:34:18.098 [main] INFO com.iluwatar.decorator.App -- A simple looking troll approaches.
11:34:18.100 [main] INFO com.iluwatar.decorator.SimpleTroll -- The troll tries to grab you!
11:34:18.100 [main] INFO com.iluwatar.decorator.SimpleTroll -- The troll shrieks in horror and runs away!
11:34:18.100 [main] INFO com.iluwatar.decorator.App -- Simple troll power: 10.
A troll with huge club surprises you.
The troll tries to grab you!
The troll swings at you with a club!
The troll shrieks in horror and runs away!
Clubbed troll power:20.
11:34:18.100 [main] INFO com.iluwatar.decorator.App -- A troll with huge club surprises you.
11:34:18.101 [main] INFO com.iluwatar.decorator.SimpleTroll -- The troll tries to grab you!
11:34:18.101 [main] INFO com.iluwatar.decorator.ClubbedTroll -- The troll swings at you with a club!
11:34:18.101 [main] INFO com.iluwatar.decorator.SimpleTroll -- The troll shrieks in horror and runs away!
11:34:18.101 [main] INFO com.iluwatar.decorator.App -- Clubbed troll power: 20.
```
## Class diagram
![alt text](./etc/decorator.urm.png "Decorator pattern class diagram")
![Decorator](./etc/decorator.urm.png "Decorator pattern class diagram")
## Applicability
@@ -144,7 +146,7 @@ Decorator is used to:
## Tutorials
* [Decorator Pattern Tutorial](https://www.journaldev.com/1540/decorator-design-pattern-in-java-example)
* [Decorator Design Pattern in Java Example (DigitalOcean)](https://www.digitalocean.com/community/tutorials/decorator-design-pattern-in-java-example)
## Known uses
@@ -177,10 +179,9 @@ Trade-offs:
## Credits
* [Design Patterns: Elements of Reusable Object-Oriented Software](https://www.amazon.com/gp/product/0201633612/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0201633612&linkCode=as2&tag=javadesignpat-20&linkId=675d49790ce11db99d90bde47f1aeb59)
* [Functional Programming in Java: Harnessing the Power of Java 8 Lambda Expressions](https://www.amazon.com/gp/product/1937785467/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=1937785467&linkCode=as2&tag=javadesignpat-20&linkId=7e4e2fb7a141631491534255252fd08b)
* [J2EE Design Patterns](https://www.amazon.com/gp/product/0596004273/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596004273&linkCode=as2&tag=javadesignpat-20&linkId=48d37c67fb3d845b802fa9b619ad8f31)
* [Head First Design Patterns: A Brain-Friendly Guide](https://www.amazon.com/gp/product/0596007124/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596007124&linkCode=as2&tag=javadesignpat-20&linkId=6b8b6eea86021af6c8e3cd3fc382cb5b)
* [Refactoring to Patterns](https://www.amazon.com/gp/product/0321213351/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0321213351&linkCode=as2&tag=javadesignpat-20&linkId=2a76fcb387234bc71b1c61150b3cc3a7)
* [J2EE Design Patterns](https://www.amazon.com/gp/product/0596004273/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596004273&linkCode=as2&tag=javadesignpat-20&linkId=f27d2644fbe5026ea448791a8ad09c94)
* [Design Patterns: Elements of Reusable Object-Oriented Software](https://amzn.to/3w0pvKI)
* [Functional Programming in Java](https://amzn.to/3JUIc5Q)
* [Head First Design Patterns: Building Extensible and Maintainable Object-Oriented Software](https://amzn.to/49NGldq)
* [J2EE Design Patterns](https://amzn.to/4dpzgmx)
* [Pattern-Oriented Software Architecture, Volume 1: A System of Patterns](https://amzn.to/4aKFTgS)
* [Refactoring to Patterns](https://amzn.to/3VOO4F5)