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Adding parameterized specification (Issue#1055) (iluwatar#1088)
* Resolution proposition to Issue#1055 (UML diagram left to do) * Deciding not to modify the UML diagram for now
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‎specification/README.md‎

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@@ -31,7 +31,7 @@ Use the Specification pattern when
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Real world example
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> There is a pool of different creatures and we often need to select some subset of them. We can write our search specification such as "creatures that can fly" and give it to the party that will perform the filtering.
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> There is a pool of different creatures and we often need to select some subset of them. We can write our search specification such as "creatures that can fly" or "creatures heavier than 500 kilograms" and give it to the party that will perform the filtering.
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In Plain Words
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@@ -43,14 +43,16 @@ Wikipedia says
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**Programmatic Example**
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If we look at our creature pool example from above, we have a set of creatures with certain properties.
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If we look at our creature pool example from above, we have a set of creatures with certain properties.\
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Those properties can be part of a pre-defined, limited set (represented here by the enums Size, Movement and Color); but they can also be discrete (e.g. the mass of a Creature). In this case, it is more appropriate to use what we call "parameterized specification", where the property value can be given as an argument when the Creature is created, allowing for more flexibility.
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```java
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public interface Creature {
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String getName();
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Size getSize();
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Movement getMovement();
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Color getColor();
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Mass getMass();
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}
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```
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@@ -60,7 +62,7 @@ And dragon implementation looks like this.
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public class Dragon extends AbstractCreature {
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public Dragon() {
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super("Dragon", Size.LARGE, Movement.FLYING, Color.RED);
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super("Dragon", Size.LARGE, Movement.FLYING, Color.RED, new Mass(39300.0));
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}
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}
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```
@@ -83,13 +85,38 @@ public class MovementSelector implements Predicate<Creature> {
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}
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```
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On the other hand, we selecting creatures heavier than a chosen amount, we use MassGreaterThanSelector.
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```java
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public class MassGreaterThanSelector implements Predicate<Creature> {
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private final Mass mass;
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public MassGreaterThanSelector(double mass) {
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this.mass = new Mass(mass);
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}
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@Override
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public boolean test(Creature t) {
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return t.getMass().greaterThan(mass);
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}
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}
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```
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With these building blocks in place, we can perform a search for red and flying creatures like this.
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```java
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List<Creature> redAndFlyingCreatures = creatures.stream()
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.filter(new ColorSelector(Color.RED).and(new MovementSelector(Movement.FLYING))).collect(Collectors.toList());
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```
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But we could also use our paramterized selector like this.
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```java
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List<Creature> heavyCreatures = creatures.stream()
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.filter(new MassGreaterThanSelector(500.0).collect(Collectors.toList());
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```
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## Related patterns
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* Repository

‎specification/etc/specification.ucls‎

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@@ -117,7 +117,7 @@
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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>
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<enumeration id="14" language="java" name="com.iluwatar.property.Color" project="specification"
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file="/specification/src/main/java/com/iluwatar/property/Color.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="1416" y="223"/>
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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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</enumeration>
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</enumeration>
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<generalization id="15">
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<end type="SOURCE" refId="1"/>
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<end type="TARGET" refId="8"/>
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<generalization id="33">
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<end type="SOURCE" refId="13"/>
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<end type="TARGET" refId="8"/>
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</generalization>
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<association id="34">
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</generalization>
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<association id="34">
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<end type="SOURCE" refId="5" navigable="false">
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<attribute id="35" name="m"/>
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<multiplicity id="36" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="12" navigable="true"/>
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<attribute id="35" name="m"/>
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<multiplicity id="36" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="12" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<association id="37">
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</end>
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<end type="TARGET" refId="14" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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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"/>

‎specification/src/main/java/com/iluwatar/specification/app/App.java‎

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import com.iluwatar.specification.creature.Shark;
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import com.iluwatar.specification.creature.Troll;
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import com.iluwatar.specification.property.Color;
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import com.iluwatar.specification.property.Mass;
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import com.iluwatar.specification.property.Movement;
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import com.iluwatar.specification.selector.ColorSelector;
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import com.iluwatar.specification.selector.MassGreaterThanSelector;
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import com.iluwatar.specification.selector.MassSmallerThanOrEqSelector;
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import com.iluwatar.specification.selector.MovementSelector;
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import java.util.List;
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import java.util.stream.Collectors;
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* <p>http://martinfowler.com/apsupp/spec.pdf</p>
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*/
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public class App {
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private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
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/**
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// initialize creatures list
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List<Creature> creatures = List.of(new Goblin(), new Octopus(), new Dragon(), new Shark(),
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new Troll(), new KillerBee());
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// so-called "hard-coded" specification
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LOGGER.info("Demonstrating hard-coded specification :");
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// find all walking creatures
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LOGGER.info("Find all walking creatures");
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List<Creature> walkingCreatures =
@@ -79,5 +84,19 @@ public static void main(String[] args) {
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.filter(new ColorSelector(Color.RED).and(new MovementSelector(Movement.FLYING)))
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.collect(Collectors.toList());
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redAndFlyingCreatures.forEach(c -> LOGGER.info(c.toString()));
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// so-called "parameterized" specification
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LOGGER.info("Demonstrating parameterized specification :");
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// find all creatures heavier than 500kg
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LOGGER.info("Find all creatures heavier than 600kg");
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List<Creature> heavyCreatures =
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creatures.stream().filter(new MassGreaterThanSelector(600.0))
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.collect(Collectors.toList());
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heavyCreatures.forEach(c -> LOGGER.info(c.toString()));
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// find all creatures heavier than 500kg
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LOGGER.info("Find all creatures lighter than or weighing exactly 500kg");
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List<Creature> lightCreatures =
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creatures.stream().filter(new MassSmallerThanOrEqSelector(500.0))
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.collect(Collectors.toList());
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lightCreatures.forEach(c -> LOGGER.info(c.toString()));
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}
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}

‎specification/src/main/java/com/iluwatar/specification/creature/AbstractCreature.java‎

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package com.iluwatar.specification.creature;
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import com.iluwatar.specification.property.Color;
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import com.iluwatar.specification.property.Mass;
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import com.iluwatar.specification.property.Movement;
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import com.iluwatar.specification.property.Size;
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private Size size;
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private Movement movement;
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private Color color;
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private Mass mass;
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/**
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* Constructor.
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*/
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public AbstractCreature(String name, Size size, Movement movement, Color color) {
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public AbstractCreature(String name, Size size, Movement movement, Color color, Mass mass) {
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this.name = name;
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this.size = size;
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this.movement = movement;
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this.color = color;
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this.mass = mass;
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}
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@Override
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public String toString() {
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return String.format("%s [size=%s, movement=%s, color=%s]", name, size, movement, color);
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return String.format("%s [size=%s, movement=%s, color=%s, mass=%s]",
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name, size, movement, color, mass);
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}
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@Override
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public Color getColor() {
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return color;
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}
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@Override
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public Mass getMass() {
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return mass;
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}
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}

‎specification/src/main/java/com/iluwatar/specification/creature/Creature.java‎

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package com.iluwatar.specification.creature;
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import com.iluwatar.specification.property.Color;
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import com.iluwatar.specification.property.Mass;
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import com.iluwatar.specification.property.Movement;
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import com.iluwatar.specification.property.Size;
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Movement getMovement();
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Color getColor();
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Mass getMass();
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}

‎specification/src/main/java/com/iluwatar/specification/creature/Dragon.java‎

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package com.iluwatar.specification.creature;
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import com.iluwatar.specification.property.Color;
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import com.iluwatar.specification.property.Mass;
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import com.iluwatar.specification.property.Movement;
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import com.iluwatar.specification.property.Size;
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public class Dragon extends AbstractCreature {
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public Dragon() {
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super("Dragon", Size.LARGE, Movement.FLYING, Color.RED);
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this(new Mass(39300.0));
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}
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public Dragon(Mass mass) {
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super("Dragon", Size.LARGE, Movement.FLYING, Color.RED, mass);
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}
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}

‎specification/src/main/java/com/iluwatar/specification/creature/Goblin.java‎

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package com.iluwatar.specification.creature;
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import com.iluwatar.specification.property.Color;
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import com.iluwatar.specification.property.Mass;
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import com.iluwatar.specification.property.Movement;
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import com.iluwatar.specification.property.Size;
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public class Goblin extends AbstractCreature {
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public Goblin() {
36-
super("Goblin", Size.SMALL, Movement.WALKING, Color.GREEN);
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this(new Mass(30.0));
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}
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public Goblin(Mass mass) {
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super("Goblin", Size.SMALL, Movement.WALKING, Color.GREEN, mass);
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}
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}

‎specification/src/main/java/com/iluwatar/specification/creature/KillerBee.java‎

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package com.iluwatar.specification.creature;
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import com.iluwatar.specification.property.Color;
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import com.iluwatar.specification.property.Mass;
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import com.iluwatar.specification.property.Movement;
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import com.iluwatar.specification.property.Size;
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public class KillerBee extends AbstractCreature {
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public KillerBee() {
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super("KillerBee", Size.SMALL, Movement.FLYING, Color.LIGHT);
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this(new Mass(6.7));
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}
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public KillerBee(Mass mass) {
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super("KillerBee", Size.SMALL, Movement.FLYING, Color.LIGHT, mass);
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}
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}

‎specification/src/main/java/com/iluwatar/specification/creature/Octopus.java‎

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package com.iluwatar.specification.creature;
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import com.iluwatar.specification.property.Color;
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import com.iluwatar.specification.property.Mass;
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import com.iluwatar.specification.property.Movement;
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import com.iluwatar.specification.property.Size;
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public class Octopus extends AbstractCreature {
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public Octopus() {
36-
super("Octopus", Size.NORMAL, Movement.SWIMMING, Color.DARK);
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this(new Mass(12.0));
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}
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public Octopus(Mass mass) {
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super("Octopus", Size.NORMAL, Movement.SWIMMING, Color.DARK, mass);
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}
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}

‎specification/src/main/java/com/iluwatar/specification/creature/Shark.java‎

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package com.iluwatar.specification.creature;
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import com.iluwatar.specification.property.Color;
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import com.iluwatar.specification.property.Mass;
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import com.iluwatar.specification.property.Movement;
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import com.iluwatar.specification.property.Size;
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public class Shark extends AbstractCreature {
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public Shark() {
36-
super("Shark", Size.NORMAL, Movement.SWIMMING, Color.LIGHT);
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this(new Mass(500.0));
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}
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public Shark(Mass mass) {
41+
super("Shark", Size.NORMAL, Movement.SWIMMING, Color.LIGHT, mass);
3742
}
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}

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