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Nicolai Parlog
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[06] Create benchmark for recreation/reuse of reg ex patterns
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‎.gitignore‎

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# Maven
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target/
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dependency-reduced-pom.xml

‎README.md‎

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# Effective Java
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This project contains examples for my [YouTube series on _Effective Java, Third Edition_](https://www.youtube.com/playlist?list=PL_-IO8LOLuNqUzvXfRCWRRJBswKEbLhgN).
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This project contains examples and benchmarks for my [YouTube series on _Effective Java, Third Edition_](https://www.youtube.com/playlist?list=PL_-IO8LOLuNqUzvXfRCWRRJBswKEbLhgN).
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To run the benchmarks:
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```
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mvn package
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java -jar target/benchmarks.jar
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```
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Related links:
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* _Enforce the singleton property with a private constructor or an enum type_
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* _Enforce noninstantiability with a private constructor_
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* _Prefer dependency injection to hardwiring resources_
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* Item 6: _Avoid creating unnecessary objects_ -
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[benchmark](src/main/java/org/codefx/demo/effective_java/_06_unnecessary_objects/StringMatches.java)

‎pom.xml‎

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<properties>
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<maven.compiler.source>10</maven.compiler.source>
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<maven.compiler.target>10</maven.compiler.target>
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<jmh-version>1.21</jmh-version>
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<uberjar-name>benchmarks</uberjar-name>
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</properties>
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<dependencies>
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<!-- main -->
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<dependency>
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<groupId>com.google.guava</groupId>
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<artifactId>guava</artifactId>
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<version>25.0-jre</version>
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</dependency>
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<!-- jmh -->
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<dependency>
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<groupId>org.openjdk.jmh</groupId>
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<artifactId>jmh-core</artifactId>
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<version>${jmh-version}</version>
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</dependency>
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<dependency>
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<groupId>org.openjdk.jmh</groupId>
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<artifactId>jmh-generator-annprocess</artifactId>
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<version>${jmh-version}</version>
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<scope>provided</scope>
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</dependency>
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</dependencies>
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<build>
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<artifactId>maven-compiler-plugin</artifactId>
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<version>3.8.0</version>
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</plugin>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-shade-plugin</artifactId>
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<version>2.2</version>
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<executions>
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<execution>
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<phase>package</phase>
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<goals>
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<goal>shade</goal>
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</goals>
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<configuration>
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<finalName>${uberjar-name}</finalName>
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<transformers>
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<transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
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<mainClass>org.openjdk.jmh.Main</mainClass>
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</transformer>
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</transformers>
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<filters>
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<filter>
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<!--
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Shading signed JARs will fail without this.
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http://stackoverflow.com/questions/999489/invalid-signature-file-when-attempting-to-run-a-jar
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-->
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<artifact>*:*</artifact>
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<excludes>
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<exclude>META-INF/*.SF</exclude>
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<exclude>META-INF/*.DSA</exclude>
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<exclude>META-INF/*.RSA</exclude>
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</excludes>
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</filter>
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</filters>
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</configuration>
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</execution>
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</executions>
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</plugin>
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</plugins>
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<pluginManagement>
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<plugins>
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<plugin>
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<artifactId>maven-clean-plugin</artifactId>
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<version>2.5</version>
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</plugin>
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<plugin>
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<artifactId>maven-deploy-plugin</artifactId>
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<version>2.8.1</version>
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</plugin>
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<plugin>
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<artifactId>maven-install-plugin</artifactId>
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<version>2.5.1</version>
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</plugin>
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<plugin>
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<artifactId>maven-jar-plugin</artifactId>
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<version>2.4</version>
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</plugin>
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<plugin>
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<artifactId>maven-javadoc-plugin</artifactId>
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<version>2.9.1</version>
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</plugin>
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<plugin>
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<artifactId>maven-resources-plugin</artifactId>
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<version>2.6</version>
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</plugin>
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<plugin>
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<artifactId>maven-site-plugin</artifactId>
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<version>3.3</version>
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</plugin>
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<plugin>
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<artifactId>maven-source-plugin</artifactId>
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<version>2.2.1</version>
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</plugin>
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<plugin>
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<artifactId>maven-surefire-plugin</artifactId>
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<version>2.22.2</version>
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</plugin>
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</plugins>
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</pluginManagement>
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</build>
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</project>

‎src/main/java/org/codefx/demo/effective_java/_06_unnecessary_objects/StringMatches.java‎

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package org.codefx.demo.effective_java._06_unnecessary_objects;
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import org.openjdk.jmh.annotations.Benchmark;
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import org.openjdk.jmh.annotations.BenchmarkMode;
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import org.openjdk.jmh.annotations.Fork;
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import org.openjdk.jmh.annotations.Measurement;
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import org.openjdk.jmh.annotations.Mode;
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import org.openjdk.jmh.annotations.OutputTimeUnit;
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import org.openjdk.jmh.annotations.Param;
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import org.openjdk.jmh.annotations.Scope;
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import org.openjdk.jmh.annotations.State;
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import org.openjdk.jmh.annotations.Warmup;
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import java.util.concurrent.TimeUnit;
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import java.util.regex.Pattern;
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@Fork(value = 3)
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@Warmup(iterations = 3, time = 1, timeUnit = TimeUnit.SECONDS)
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@Measurement(iterations = 3, time = 1, timeUnit = TimeUnit.SECONDS)
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@BenchmarkMode(Mode.AverageTime)
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@OutputTimeUnit(TimeUnit.MICROSECONDS)
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@State(Scope.Thread)
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public class StringMatches {
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private static final String ROMAN_REG_EX = "^(?=.)M*(C[MD]|D?C{0,3})(X[CL]|L?X{0,3})(I[XV]|V?I{0,3})$";
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private static final Pattern ROMAN_PATTERN = Pattern.compile(ROMAN_REG_EX);
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@Param({ "I", "XXXIV", "_" })
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private String numeral = "I";
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@Benchmark
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public boolean recreatePatternOnEachMatch() {
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return numeral.matches(ROMAN_REG_EX);
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}
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@Benchmark
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public boolean reusePattern() {
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return ROMAN_PATTERN.matcher(numeral).matches();
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}
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}

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