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added Property pattern

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vehpsr 2015-03-29 23:03:06 +03:00
parent eddf2e630f
commit d57da2593b
10 changed files with 303 additions and 3 deletions
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14
README.md
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@ -15,8 +15,9 @@ Creational design patterns abstract the instantiation process. They help make a
* [Builder](#builder)
* [Factory Method](#factory-method)
* [Prototype](#prototype)
* [Property](#property)
* [Singleton](#singleton)
### Structural Patterns
Structural patterns are concerned with how classes and objects are composed to form larger structures.
@ -433,6 +434,17 @@ Behavioral patterns are concerned with algorithms and the assignment of responsi
**Applicability:** Use the Execute Around idiom when
* You use an API that requires methods to be called in pairs such as open/close or allocate/deallocate.
## <a name="property">Property</a> [&#8593;](#list-of-design-patterns)
**Intent:** Create hierarchy of objects and new objects using already existing objects as parents.
![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/property/etc/property.jpg "Property")
**Applicability:** Use the Property pattern when
* when you like to have objects with dynamic set of fields and prototype inheritance
**Real world examples:**
* [JavaScript](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain) prototype inheritance
# Frequently asked questions
**<a id="Q1">Q: What is the difference between State and Strategy patterns?</a>**

5
pom.xml
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@ -41,8 +41,9 @@
<module>null-object</module>
<module>event-aggregator</module>
<module>callback</module>
<module>execute-around</module>
</modules>
<module>execute-around</module>
<module>property</module>
</modules>
<dependencyManagement>
<dependencies>

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property/etc/property.ucls Normal file
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@ -0,0 +1,70 @@
<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.1.8" icons="true" automaticImage="JPEG" always-add-relationships="false"
generalizations="true" realizations="true" associations="true" dependencies="false" nesting-relationships="true">
<class id="1" language="java" name="com.iluwatar.Character" project="property"
file="/property/src/main/java/com/iluwatar/Character.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="497" y="232"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<enumeration id="2" language="java" name="com.iluwatar.Character.Type" project="property"
file="/property/src/main/java/com/iluwatar/Character.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="320" y="231"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</enumeration>
<enumeration id="3" language="java" name="com.iluwatar.Stats" project="property"
file="/property/src/main/java/com/iluwatar/Stats.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="695" y="205"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</enumeration>
<interface id="4" language="java" name="com.iluwatar.Prototype" project="property"
file="/property/src/main/java/com/iluwatar/Prototype.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="495" y="487"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</interface>
<association id="5">
<end type="SOURCE" refId="1" navigable="false">
<attribute id="6" name="type"/>
<multiplicity id="7" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="2" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<association id="8">
<end type="SOURCE" refId="1" navigable="false">
<attribute id="9" name="prototype"/>
<multiplicity id="10" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="4" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<nesting id="11">
<end type="SOURCE" refId="1"/>
<end type="TARGET" refId="2"/>
</nesting>
<realization id="12">
<end type="SOURCE" refId="1"/>
<end type="TARGET" refId="4"/>
</realization>
<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</classifier-display>
<association-display labels="true" multiplicity="true"/>
</class-diagram>

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property/pom.xml Normal file
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@ -0,0 +1,18 @@
<?xml version="1.0"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>property</artifactId>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>

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property/src/main/java/com/iluwatar/App.java Normal file
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@ -0,0 +1,49 @@
package com.iluwatar;
import com.iluwatar.Character.Type;
/**
* Example of Character instantiation using Property pattern (as concept also known like Prototype inheritance).
* In prototype inheritance instead of classes, as opposite to Java class inheritance,
* objects are used to create another objects and object hierarchies.
* Hierarchies are created using prototype chain through delegation: every object has link to parent object.
* Any base (parent) object can be amended at runtime (by adding or removal of some property), and all child objects will be affected as result.
*/
public class App {
public static void main(String[] args) {
/* set up */
Prototype charProto = new Character();
charProto.set(Stats.STRENGTH, 10);
charProto.set(Stats.AGILITY, 10);
charProto.set(Stats.ARMOR, 10);
charProto.set(Stats.ATTACK_POWER, 10);
Character mageProto = new Character(Type.MAGE, charProto);
mageProto.set(Stats.INTELLECT, 15);
mageProto.set(Stats.SPIRIT, 10);
Character warProto = new Character(Type.WARRIOR, charProto);
warProto.set(Stats.RAGE, 15);
warProto.set(Stats.ARMOR, 15); // boost default armor for warrior
Character rogueProto = new Character(Type.ROGUE, charProto);
rogueProto.set(Stats.ENERGY, 15);
rogueProto.set(Stats.AGILITY, 15); // boost default agility for rogue
/* usage */
Character mag = new Character("Player_1", mageProto);
mag.set(Stats.ARMOR, 8);
System.out.println(mag);
Character warrior = new Character("Player_2", warProto);
System.out.println(warrior);
Character rogue = new Character("Player_3", rogueProto);
System.out.println(rogue);
Character rogueDouble = new Character("Player_4", rogue);
rogueDouble.set(Stats.ATTACK_POWER, 12);
System.out.println(rogueDouble);
}
}

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property/src/main/java/com/iluwatar/Character.java Normal file
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@ -0,0 +1,117 @@
package com.iluwatar;
import java.util.HashMap;
import java.util.Map;
/**
* Represents Character in game and his abilities (base stats).
*/
public class Character implements Prototype {
public enum Type {
WARRIOR, MAGE, ROGUE
}
private final Prototype prototype;
private final Map<Stats, Integer> properties = new HashMap<>();
private String name;
private Type type;
public Character() {
this.prototype = new Prototype() { // Null-value object
@Override
public Integer get(Stats stat) {
return null;
}
@Override
public boolean has(Stats stat) {
return false;
}
@Override
public void set(Stats stat, Integer val) {
}
@Override
public void remove(Stats stat) {
}}
;
}
public Character(Type type, Prototype prototype) {
this.type = type;
this.prototype = prototype;
}
public Character(String name, Character prototype) {
this.name = name;
this.type = prototype.type;
this.prototype = prototype;
}
public String name() {
return name;
}
public Type type() {
return type;
}
@Override
public Integer get(Stats stat) {
boolean containsValue = properties.containsKey(stat);
if (containsValue) {
return properties.get(stat);
} else {
return prototype.get(stat);
}
}
@Override
public boolean has(Stats stat) {
return get(stat) != null;
}
@Override
public void set(Stats stat, Integer val) {
properties.put(stat, val);
}
@Override
public void remove(Stats stat) {
properties.put(stat, null);
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
if (name != null) {
builder
.append("Player: ")
.append(name)
.append("\n");
}
if (type != null) {
builder
.append("Character type: ")
.append(type.name())
.append("\n");
}
builder.append("Stats:\n");
for (Stats stat : Stats.values()) {
Integer value = this.get(stat);
if (value == null) {
continue;
}
builder
.append(" - ")
.append(stat.name())
.append(":")
.append(value)
.append("\n");
}
return builder.toString();
}
}

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property/src/main/java/com/iluwatar/Prototype.java Normal file
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@ -0,0 +1,12 @@
package com.iluwatar;
/**
* Interface for prototype inheritance
*/
public interface Prototype {
public Integer get(Stats stat);
public boolean has(Stats stat);
public void set(Stats stat, Integer val);
public void remove(Stats stat);
}

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property/src/main/java/com/iluwatar/Stats.java Normal file
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@ -0,0 +1,9 @@
package com.iluwatar;
/**
* All possible attributes that Character can have
*/
public enum Stats {
AGILITY, STRENGTH, ATTACK_POWER, ARMOR, INTELLECT, SPIRIT, ENERGY, RAGE
}

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property/src/test/java/com/iluwatar/AppTest.java Normal file
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@ -0,0 +1,12 @@
package com.iluwatar;
import org.junit.Test;
public class AppTest {
@Test
public void test() {
String[] args = {};
App.main(args);
}
}