Added class diagram.

Author: iluwatar

object-pool/etc/object-pool.png

@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true" 
+  realizations="true" associations="true" dependencies="false" nesting-relationships="true">  
+  <class id="1" language="java" name="com.iluwatar.ObjectPool" project="object-pool" 
+    file="/object-pool/src/main/java/com/iluwatar/ObjectPool.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="133" y="239"/>    
+    <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>  
+  <class id="2" language="java" name="com.iluwatar.OliphauntPool" project="object-pool" 
+    file="/object-pool/src/main/java/com/iluwatar/OliphauntPool.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="133" y="423"/>    
+    <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>  
+  <class id="3" language="java" name="com.iluwatar.Oliphaunt" project="object-pool" 
+    file="/object-pool/src/main/java/com/iluwatar/Oliphaunt.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="153" width="102" x="250" y="145"/>    
+    <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>  
+  <generalization id="4">    
+    <end type="SOURCE" refId="2"/>    
+    <end type="TARGET" refId="1"/>  
+  </generalization>  
+  <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>