categories:Structural

language:en

tags:

-GangOf Four

-Gangof Four

-Extensibility

Realworld example

Real-world example

}

Next we want to add club for the troll. We can do it dynamically by using a decorator:

Next, we want to add a club for the troll. We can do it dynamically by using a decorator:

LOGGER.info("A simple looking troll approaches.");

var troll=newSimpleTroll();

troll.attack();// The troll tries to grab you!

troll.fleeBattle();// The troll shrieks in horror and runs away!

troll.attack();

troll.fleeBattle();

LOGGER.info("Simple troll power: {}.\n", troll.getAttackPower());

LOGGER.info("A troll with huge club surprises you.");

var clubbedTroll=newClubbedTroll(troll);

clubbedTroll.attack();// The troll tries to grab you! The troll swings at you with a club!

clubbedTroll.fleeBattle();// The troll shrieks in horror and runs away!

clubbedTroll.attack();

clubbedTroll.fleeBattle();

LOGGER.info("Clubbed troll power: {}.\n", clubbedTroll.getAttackPower());

Program output:

A simple looking troll approaches.

The troll tries to grab you!

The troll shrieks in horror and runs away!

The troll tries to grab you!The troll swings at you with a club!

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.

are possible and would produce an explosion of subclasses to support every combination. Or a class

definition may be hidden or otherwise unavailable for subclassing.

*[Decorator Pattern Tutorial](https://www.journaldev.com/1540/decorator-design-pattern-in-java-example)

*[java.io.InputStream](http://docs.oracle.com/javase/8/docs/api/java/io/InputStream.html),[java.io.OutputStream](http://docs.oracle.com/javase/8/docs/api/java/io/OutputStream.html),

[java.io.Reader](http://docs.oracle.com/javase/8/docs/api/java/io/Reader.html) and[java.io.Writer](http://docs.oracle.com/javase/8/docs/api/java/io/Writer.html)

vartroll =newSimpleTroll();

troll.attack();

troll.fleeBattle();

LOGGER.info("Simple troll power {}.\n",troll.getAttackPower());

LOGGER.info("Simple troll power: {}.\n",troll.getAttackPower());

LOGGER.info("A troll with huge club surprises you.");

varclubbedTroll =newClubbedTroll(troll);

clubbedTroll.attack();

clubbedTroll.fleeBattle();

LOGGER.info("Clubbed troll power {}.\n",clubbedTroll.getAttackPower());

LOGGER.info("Clubbed troll power: {}.\n",clubbedTroll.getAttackPower());

}

}