added Property pattern

README.md

@@ -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>**

pom.xml

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

property/etc/property.ucls

@@ -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>

property/pom.xml

@@ -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>

property/src/main/java/com/iluwatar/App.java

@@ -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);
+	}
+}

property/src/main/java/com/iluwatar/Character.java

@@ -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();
+	}
+
+}

property/src/main/java/com/iluwatar/Prototype.java

@@ -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);
+}

property/src/main/java/com/iluwatar/Stats.java

@@ -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
+}

property/src/test/java/com/iluwatar/AppTest.java

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