Update README.md
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Ilkka Seppälä
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---
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## Also known as
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Policy
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## Intent
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Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary
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independently from clients that use it.
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Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets
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the algorithm vary independently from clients that use it.
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## Explanation
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Real world example
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> Slaying dragons is a dangerous profession. With experience it becomes easier. Veteran dragonslayers have developed different fighting strategies against different types of dragons.
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> Slaying dragons is a dangerous job. With experience it becomes easier. Veteran
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> dragonslayers have developed different fighting strategies against different types of dragons.
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In plain words
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@ -27,7 +30,8 @@ In plain words
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Wikipedia says
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> In computer programming, the strategy pattern (also known as the policy pattern) is a behavioral software design pattern that enables selecting an algorithm at runtime.
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> In computer programming, the strategy pattern (also known as the policy pattern) is a behavioral
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> software design pattern that enables selecting an algorithm at runtime.
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**Programmatic Example**
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@ -71,7 +75,8 @@ public class SpellStrategy implements DragonSlayingStrategy {
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}
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```
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And here is the mighty dragonslayer who is able to pick his fighting strategy based on the opponent.
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And here is the mighty dragonslayer, who is able to pick his fighting strategy based on the
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opponent.
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```java
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public class DragonSlayer {
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@ -92,7 +97,7 @@ public class DragonSlayer {
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}
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```
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Finally here's dragonslayer in action.
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Finally here's the dragonslayer in action.
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```java
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LOGGER.info("Green dragon spotted ahead!");
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@ -104,19 +109,25 @@ Finally here's dragonslayer in action.
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LOGGER.info("Black dragon lands before you.");
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dragonSlayer.changeStrategy(new SpellStrategy());
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dragonSlayer.goToBattle();
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// Green dragon spotted ahead!
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// With your Excalibur you sever the dragon's head!
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// Red dragon emerges.
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// You shoot the dragon with the magical crossbow and it falls dead on the ground!
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// Black dragon lands before you.
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// You cast the spell of disintegration and the dragon vaporizes in a pile of dust!
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```
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Program output:
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```
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Green dragon spotted ahead!
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With your Excalibur you sever the dragon's head!
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Red dragon emerges.
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You shoot the dragon with the magical crossbow and it falls dead on the ground!
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Black dragon lands before you.
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You cast the spell of disintegration and the dragon vaporizes in a pile of dust!
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```
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## Class diagram
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## Applicability
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Use the Strategy pattern when
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* Many related classes differ only in their behavior. Strategies provide a way to configure a class either one of many behaviors
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<?xml version="1.0" encoding="UTF-8"?>
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<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
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realizations="true" associations="true" dependencies="false" nesting-relationships="true">
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<interface id="1" language="java" name="com.iluwatar.strategy.DragonSlayingStrategy" project="strategy"
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file="/strategy/src/main/java/com/iluwatar/strategy/DragonSlayingStrategy.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="88" width="186" x="525" y="428"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</interface>
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<class id="2" language="java" name="com.iluwatar.strategy.ProjectileStrategy" project="strategy"
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file="/strategy/src/main/java/com/iluwatar/strategy/ProjectileStrategy.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="106" width="151" x="218" y="264"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<class id="3" language="java" name="com.iluwatar.strategy.SpellStrategy" project="strategy"
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file="/strategy/src/main/java/com/iluwatar/strategy/SpellStrategy.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="106" width="125" x="409" y="264"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<class id="4" language="java" name="com.iluwatar.strategy.DragonSlayer" project="strategy"
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file="/strategy/src/main/java/com/iluwatar/strategy/DragonSlayer.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="124" width="284" x="574" y="264"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<class id="5" language="java" name="com.iluwatar.strategy.MeleeStrategy" project="strategy"
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file="/strategy/src/main/java/com/iluwatar/strategy/MeleeStrategy.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="106" width="127" x="898" y="264"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<realization id="6">
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<end type="SOURCE" refId="5"/>
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<end type="TARGET" refId="1"/>
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</realization>
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<realization id="7">
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<end type="SOURCE" refId="2"/>
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<end type="TARGET" refId="1"/>
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</realization>
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<realization id="8">
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<end type="SOURCE" refId="3"/>
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<end type="TARGET" refId="1"/>
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</realization>
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<association id="9">
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<end type="SOURCE" refId="4" navigable="false">
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<attribute id="10" name="strategy"/>
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<multiplicity id="11" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="1" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</classifier-display>
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<association-display labels="true" multiplicity="true"/>
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</class-diagram>
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