#590 Add explanation for Prototype
This commit is contained in:
Ilkka Seppälä
parent
f6c8bfbc39
commit
b639f3630e
1
pom.xml
1
pom.xml
@ -464,6 +464,7 @@
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<param>factory-method</param>
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<param>abstract-factory</param>
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<param>builder</param>
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<param>prototype</param>
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</skipForProjects>
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</configuration>
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</plugin>
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@ -15,14 +15,57 @@ tags:
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Specify the kinds of objects to create using a prototypical
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instance, and create new objects by copying this prototype.
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## Explanation
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Real world example
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> Remember Dolly? The sheep that was cloned! Lets not get into the details but the key point here is that it is all about cloning.
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In plain words
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> Create object based on an existing object through cloning.
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Wikipedia says
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> The prototype pattern is a creational design pattern in software development. It is used when the type of objects to create is determined by a prototypical instance, which is cloned to produce new objects.
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In short, it allows you to create a copy of an existing object and modify it to your needs, instead of going through the trouble of creating an object from scratch and setting it up.
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**Programmatic Example**
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In Java, it can be easily done by implementing `Cloneable` and overriding `clone` from `Object`
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```
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class Sheep implements Cloneable {
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privage String name;
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public Sheep(String name) { this.name = name; }
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public void setName(String name) { this.name = name; }
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public String getName() { return name; }
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@Override
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public Sheep clone() throws CloneNotSupportedException {
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return new Sheep(name);
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}
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}
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```
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Then it can be cloned like below
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```
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Sheep original = new Sheep("Jolly");
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System.out.println(original.getName()); // Jolly
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// Clone and modify what is required
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Sheep cloned = original.clone();
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cloned.setName("Dolly");
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System.out.println(cloned.getName()); // Dolly
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```
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## Applicability
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Use the Prototype pattern when a system should be independent of how its products are created, composed and represented; and
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* when the classes to instantiate are specified at run-time, for example, by dynamic loading; or
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* to avoid building a class hierarchy of factories that parallels the class hierarchy of products; or
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* when the classes to instantiate are specified at run-time, for example, by dynamic loading
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* to avoid building a class hierarchy of factories that parallels the class hierarchy of products
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* when instances of a class can have one of only a few different combinations of state. It may be more convenient to install a corresponding number of prototypes and clone them rather than instantiating the class manually, each time with the appropriate state
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* when object creation is expensive compared to cloning
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## Real world examples
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@ -1,182 +0,0 @@
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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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<class id="1" language="java" name="com.iluwatar.prototype.ElfMage" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/ElfMage.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="142" width="132" x="788" y="192"/>
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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="2" language="java" name="com.iluwatar.prototype.OrcMage" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/OrcMage.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="142" width="140" x="960" y="192"/>
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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.prototype.Mage" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/Mage.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="105" width="132" x="665" y="28"/>
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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.prototype.Prototype" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/Prototype.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="105" width="132" x="493" y="-154"/>
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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.prototype.Beast" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/Beast.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="105" width="132" x="321" y="28"/>
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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="6" language="java" name="com.iluwatar.prototype.ElfWarlord" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/ElfWarlord.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="142" width="154" x="388" y="192"/>
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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="7" language="java" name="com.iluwatar.prototype.Warlord" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/Warlord.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="105" width="132" x="493" y="28"/>
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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="8" language="java" name="com.iluwatar.prototype.ElfBeast" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/ElfBeast.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="142" width="132" x="32" y="192"/>
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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="9" language="java" name="com.iluwatar.prototype.OrcWarlord" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/OrcWarlord.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="142" width="166" x="582" y="192"/>
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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="10" language="java" name="com.iluwatar.prototype.HeroFactoryImpl" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/HeroFactoryImpl.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="142" width="248" x="665" y="-154"/>
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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="11" language="java" name="com.iluwatar.prototype.OrcBeast" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/OrcBeast.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="142" width="144" x="204" y="192"/>
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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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<interface id="12" language="java" name="com.iluwatar.prototype.HeroFactory" project="prototype"
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file="/prototype/src/main/java/com/iluwatar/prototype/HeroFactory.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="124" width="164" x="837" y="28"/>
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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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<generalization id="13">
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<end type="SOURCE" refId="8"/>
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<end type="TARGET" refId="5"/>
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</generalization>
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<generalization id="14">
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<end type="SOURCE" refId="6"/>
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<end type="TARGET" refId="7"/>
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</generalization>
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<generalization id="15">
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<end type="SOURCE" refId="7"/>
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<end type="TARGET" refId="4"/>
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</generalization>
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<association id="16">
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<end type="SOURCE" refId="10" navigable="false">
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<attribute id="17" name="beast"/>
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<multiplicity id="18" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="5" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<realization id="19">
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<end type="SOURCE" refId="10"/>
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<end type="TARGET" refId="12"/>
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</realization>
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<generalization id="20">
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<end type="SOURCE" refId="9"/>
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<end type="TARGET" refId="7"/>
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</generalization>
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<generalization id="21">
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<end type="SOURCE" refId="1"/>
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<end type="TARGET" refId="3"/>
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</generalization>
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<generalization id="22">
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<end type="SOURCE" refId="5"/>
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<end type="TARGET" refId="4"/>
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</generalization>
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<association id="23">
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<end type="SOURCE" refId="10" navigable="false">
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<attribute id="24" name="mage"/>
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<multiplicity id="25" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="3" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<association id="26">
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<end type="SOURCE" refId="10" navigable="false">
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<attribute id="27" name="warlord"/>
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<multiplicity id="28" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="7" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<generalization id="29">
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<end type="SOURCE" refId="2"/>
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<end type="TARGET" refId="3"/>
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</generalization>
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<generalization id="30">
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<end type="SOURCE" refId="3"/>
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<end type="TARGET" refId="4"/>
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</generalization>
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<generalization id="31">
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<end type="SOURCE" refId="11"/>
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<end type="TARGET" refId="5"/>
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</generalization>
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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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@ -1,82 +0,0 @@
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@startuml
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package com.iluwatar.prototype {
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class App {
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- LOGGER : Logger {static}
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+ App()
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+ main(args : String[]) {static}
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}
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abstract class Beast {
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+ Beast()
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+ clone() : Beast {abstract}
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}
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class ElfBeast {
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+ ElfBeast()
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+ clone() : Beast
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+ toString() : String
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}
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class ElfMage {
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+ ElfMage()
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+ clone() : Mage
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+ toString() : String
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}
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class ElfWarlord {
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+ ElfWarlord()
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+ clone() : Warlord
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+ toString() : String
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}
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interface HeroFactory {
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+ createBeast() : Beast {abstract}
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+ createMage() : Mage {abstract}
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+ createWarlord() : Warlord {abstract}
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}
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class HeroFactoryImpl {
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- beast : Beast
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- mage : Mage
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- warlord : Warlord
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+ HeroFactoryImpl(mage : Mage, warlord : Warlord, beast : Beast)
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+ createBeast() : Beast
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+ createMage() : Mage
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+ createWarlord() : Warlord
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}
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abstract class Mage {
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+ Mage()
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+ clone() : Mage {abstract}
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}
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class OrcBeast {
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+ OrcBeast()
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+ clone() : Beast
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+ toString() : String
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}
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class OrcMage {
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+ OrcMage()
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+ clone() : Mage
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+ toString() : String
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}
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class OrcWarlord {
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+ OrcWarlord()
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+ clone() : Warlord
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+ toString() : String
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}
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abstract class Prototype {
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+ Prototype()
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+ clone() : Object {abstract}
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}
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abstract class Warlord {
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+ Warlord()
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+ clone() : Warlord {abstract}
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}
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}
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HeroFactoryImpl --> "-beast" Beast
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HeroFactoryImpl --> "-warlord" Warlord
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HeroFactoryImpl --> "-mage" Mage
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Beast --|> Prototype
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ElfBeast --|> Beast
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ElfMage --|> Mage
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ElfWarlord --|> Warlord
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HeroFactoryImpl ..|> HeroFactory
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Mage --|> Prototype
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OrcBeast --|> Beast
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OrcMage --|> Mage
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OrcWarlord --|> Warlord
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Warlord --|> Prototype
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@enduml
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Before Width: | Height: | Size: 95 KiB |
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Block a user