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* 'master' of https://github.com/iluwatar/java-design-patterns: (27 commits) Remove use of coveralls-maven-plugin (sonarqube.com covers this) Add SonarQube.com badge Fix environment variable Add Travis instructions for SonarQube.com analysis Adds more criticism to Singleton pattern. Event Based Asynchronous pattern: Add missing license header and puml diagram Changed config to non-interactive Moved config into a separate dir Unused import removed. End process logic clause has been corrected. Caching pattern: Documentation and diagram Fixes iluwatar#437. Adds criticism to Singleton pattern. Alter JUnit tests to run in lesser time. Updated version snapshot to 1.14.0 Changes based on review feedback. Closes iluwatar#436. Adds criticism to service locator pattern. Caching pattern: Implementation of Cache-Aside pattern Caching pattern: Style fix for null check Caching pattern: Refactor LRU cache to avoid NPE and unnecessary cache lookup Caching pattern: Refactor shutdown hook to use method reference ...
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‎.travis.yml‎

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@@ -6,6 +6,7 @@ env:
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global:
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- GH_REF: github.com/iluwatar/java-design-patterns.git
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- secure: LxTDuNS/rBWIvKkaEqr79ImZAe48mCdoYCF41coxNXgNoippo4GIBArknqtv+XvdkiuRZ1yGyj6pn8GU33c/yn+krddTUkVCwTbVatbalW5jhQjDbHYym/JcxaK9ZS/3JTeGcWrBgiPqHEEDhCf26vPZsXoMSeVCEORVKTp1BSg=
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- secure: "eoWlW9GyTJY04P8K3pxayXwU9/hmptQg/LfirispQkV9YvmziCfSzXnatnBhNfud98sCzY8BScXnb+OWLTnjLKpId4rtEqb0aJ40Jc32cUKzgzFAUn7cNcDAbUIfyPAGVqyQqfj/11wYSADwWMMOPlW97ExUtoyiH2WenXuRHso="
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before_install:
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- export DISPLAY=:99.0
@@ -16,7 +17,7 @@ install:
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- mvn install -DskipTests=true -Dmaven.javadoc.skip=true -B -V -e
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after_success:
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- mvn clean test jacoco:report coveralls:report
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- mvn clean org.jacoco:jacoco-maven-plugin:prepare-agent package sonar:sonar -Dsonar.host.url=https://sonarqube.com -Dsonar.login=$SONAR_TOKEN
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- bash update-ghpages.sh
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# use latest java version available instead of travis default

‎README.md‎

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# Design patterns implemented in Java
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[![Build status](https://travis-ci.org/iluwatar/java-design-patterns.svg?branch=master)](https://travis-ci.org/iluwatar/java-design-patterns)
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[![Coverage Status](https://coveralls.io/repos/iluwatar/java-design-patterns/badge.svg?branch=master)](https://coveralls.io/r/iluwatar/java-design-patterns?branch=master)
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[![License MIT](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/iluwatar/java-design-patterns/master/LICENSE.md)
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[![Join the chat at https://gitter.im/iluwatar/java-design-patterns](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
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[![Quality Gate](https://sonarqube.com/api/badges/gate?key=com.iluwatar%3Ajava-design-patterns)](https://sonarqube.com/dashboard/index/com.iluwatar%3Ajava-design-patterns)
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# Introduction
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‎async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutor.java‎

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@@ -57,12 +57,10 @@ public <T> AsyncResult<T> startProcess(Callable<T> task, AsyncCallback<T> callba
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@Override
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public <T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException {
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if (asyncResult.isCompleted()) {
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return asyncResult.getValue();
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} else {
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if (!asyncResult.isCompleted()) {
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asyncResult.await();
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return asyncResult.getValue();
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}
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return asyncResult.getValue();
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}
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/**

‎async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutorTest.java‎

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import java.util.concurrent.ExecutionException;
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import static org.junit.Assert.*;
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import static org.mockito.Matchers.eq;
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import static org.mockito.Mockito.*;
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import static org.mockito.internal.verification.VerificationModeFactory.times;
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‎caching/README.md‎

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* [Write-through, write-around, write-back: Cache explained](http://www.computerweekly.com/feature/Write-through-write-around-write-back-Cache-explained)
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* [Read-Through, Write-Through, Write-Behind, and Refresh-Ahead Caching](https://docs.oracle.com/cd/E15357_01/coh.360/e15723/cache_rtwtwbra.htm#COHDG5177)
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* [Cache-Aside](https://msdn.microsoft.com/en-us/library/dn589799.aspx)

‎caching/etc/caching.png‎

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‎caching/etc/caching.ucls‎

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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="main.java.com.wssia.caching.App" project="CachingPatterns"
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file="/CachingPatterns/src/main/java/com/wssia/caching/App.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="249" y="150"/>
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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-diagram version="1.1.11" icons="true" automaticImage="PNG" always-add-relationships="false"
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generalizations="true" realizations="true" associations="true" dependencies="false" nesting-relationships="true"
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router="FAN">
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<class id="1" language="java" name="com.iluwatar.caching.CacheStore" project="caching"
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file="/caching/src/main/java/com/iluwatar/caching/CacheStore.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="322" y="444"/>
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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.caching.LruCache" project="caching"
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file="/caching/src/main/java/com/iluwatar/caching/LruCache.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="700" y="446"/>
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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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<enumeration id="3" language="java" name="com.iluwatar.caching.CachingPolicy" project="caching"
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file="/caching/src/main/java/com/iluwatar/caching/CachingPolicy.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="943" y="122"/>
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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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</enumeration>
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<class id="4" language="java" name="com.iluwatar.caching.DbManager" project="caching"
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file="/caching/src/main/java/com/iluwatar/caching/DbManager.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="1011" y="426"/>
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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.caching.App" project="caching"
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file="/caching/src/main/java/com/iluwatar/caching/App.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="304" y="95"/>
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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.caching.AppManager" project="caching"
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file="/caching/src/main/java/com/iluwatar/caching/AppManager.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="604" y="122"/>
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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.caching.UserAccount" project="caching"
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file="/caching/src/main/java/com/iluwatar/caching/UserAccount.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="1161" y="139"/>
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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="main.java.com.wssia.caching.AppManager" project="CachingPatterns"
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file="/CachingPatterns/src/main/java/com/wssia/caching/AppManager.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="502" y="163"/>
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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="main.java.com.wssia.caching.CacheStore" project="CachingPatterns"
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file="/CachingPatterns/src/main/java/com/wssia/caching/CacheStore.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="537" y="436"/>
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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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<enumeration id="4" language="java" name="main.java.com.wssia.caching.CachingPolicy" project="CachingPatterns"
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file="/CachingPatterns/src/main/java/com/wssia/caching/CachingPolicy.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="789" y="162"/>
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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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</enumeration>
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<class id="5" language="java" name="main.java.com.wssia.caching.DBManager" project="CachingPatterns"
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file="/CachingPatterns/src/main/java/com/wssia/caching/DBManager.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="1137" y="134"/>
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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="main.java.com.wssia.caching.LRUCache" project="CachingPatterns"
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file="/CachingPatterns/src/main/java/com/wssia/caching/LRUCache.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="884" y="435"/>
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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="main.java.com.wssia.caching.UserAccount" project="CachingPatterns"
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file="/CachingPatterns/src/main/java/com/wssia/caching/UserAccount.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="1140" y="405"/>
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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="test.java.com.wssia.caching.AppTest" project="CachingPatterns"
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file="/CachingPatterns/src/test/java/com/wssia/caching/AppTest.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="251" y="374"/>
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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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<association id="9">
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<end type="SOURCE" refId="2" navigable="false">
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<attribute id="10" name="cachingPolicy"/>
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<multiplicity id="11" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="4" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<association id="12">
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<end type="SOURCE" refId="8" navigable="false">
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<attribute id="13" name="app"/>
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<multiplicity id="14" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="1" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<association id="15">
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<end type="SOURCE" refId="3" navigable="false">
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<attribute id="16" name="cache"/>
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<multiplicity id="17" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="6" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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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"/>
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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 id="8">
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<end type="SOURCE" refId="1" navigable="false">
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<attribute id="9" name="cache"/>
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<multiplicity id="10" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="2" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<association id="11">
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<end type="SOURCE" refId="6" navigable="false">
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<attribute id="12" name="cachingPolicy"/>
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<multiplicity id="13" 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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<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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</class-diagram>

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

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*
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* The Caching pattern describes how to avoid expensive re-acquisition of resources by not releasing
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* the resources immediately after their use. The resources retain their identity, are kept in some
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* fast-access storage, and are re-used to avoid having to acquire them again. There are three main
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* caching strategies/techniques in this pattern; each with their own pros and cons. They are:
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* fast-access storage, and are re-used to avoid having to acquire them again. There are four main
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* caching strategies/techniques in this pattern; each with their own pros and cons. They are;
3434
* <code>write-through</code> which writes data to the cache and DB in a single transaction,
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* <code>write-around</code> which writes data immediately into the DB instead of the cache, and
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* <code>write-around</code> which writes data immediately into the DB instead of the cache,
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* <code>write-behind</code> which writes data into the cache initially whilst the data is only
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* written into the DB when the cache is full. The <code>read-through</code> strategy is also
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* included in the mentioned three strategies -- returns data from the cache to the caller <b>if</b>
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* it exists <b>else</b> queries from DB and stores it into the cache for future use. These
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* strategies determine when the data in the cache should be written back to the backing store (i.e.
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* Database) and help keep both data sources synchronized/up-to-date. This pattern can improve
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* performance and also helps to maintain consistency between data held in the cache and the data in
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* the underlying data store.
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* written into the DB when the cache is full, and <code>cache-aside</code> which pushes the
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* responsibility of keeping the data synchronized in both data sources to the application itself.
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* The <code>read-through</code> strategy is also included in the mentioned four strategies --
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* returns data from the cache to the caller <b>if</b> it exists <b>else</b> queries from DB and
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* stores it into the cache for future use. These strategies determine when the data in the cache
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* should be written back to the backing store (i.e. Database) and help keep both data sources
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* synchronized/up-to-date. This pattern can improve performance and also helps to maintain
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* consistency between data held in the cache and the data in the underlying data store.
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* <p>
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* In this example, the user account ({@link UserAccount}) entity is used as the underlying
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* application data. The cache itself is implemented as an internal (Java) data structure. It adopts
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* a Least-Recently-Used (LRU) strategy for evicting data from itself when its full. The three
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* a Least-Recently-Used (LRU) strategy for evicting data from itself when its full. The four
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* strategies are individually tested. The testing of the cache is restricted towards saving and
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* {@link App} is not aware of the underlying mechanics of the application (i.e. save and query) and
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app.useReadAndWriteThroughStrategy();
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app.useReadThroughAndWriteAroundStrategy();
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app.useReadThroughAndWriteBehindStrategy();
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app.useCacheAsideStategy();
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}
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/**
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AppManager.find("004");
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}
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/**
149+
* Cache-Aside
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*/
151+
public void useCacheAsideStategy() {
152+
System.out.println("# CachingPolicy.ASIDE");
153+
AppManager.initCachingPolicy(CachingPolicy.ASIDE);
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System.out.println(AppManager.printCacheContent());
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UserAccount userAccount3 = new UserAccount("003", "Adam", "He likes food.");
157+
UserAccount userAccount4 = new UserAccount("004", "Rita", "She hates cats.");
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UserAccount userAccount5 = new UserAccount("005", "Isaac", "He is allergic to mustard.");
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AppManager.save(userAccount3);
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AppManager.save(userAccount4);
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AppManager.save(userAccount5);
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System.out.println(AppManager.printCacheContent());
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AppManager.find("003");
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System.out.println(AppManager.printCacheContent());
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AppManager.find("004");
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System.out.println(AppManager.printCacheContent());
168+
}
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}

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