JMH Micro-benchmark for StackOverflow question http://stackoverflow.com/questions/42627108/best-way-to-convert-iterablecharacter-to-string . Build with "mvn clean install", run with "java -jar target.benchmarks.jar"

CharsToString.java

package com.stackoverflow.q42627108;

import com.google.common.base.Joiner;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Param;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Warmup;
import org.openjdk.jmh.infra.Blackhole;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;

import static org.openjdk.jmh.annotations.Mode.Throughput;

public class CharsToString {

    @State(Scope.Benchmark)
    public static class Params {
        @Param
        public Mode mode;

        @Param({"10", "100","1000","100000"})
        public int size;

        @Setup
        public void prepare() {
            List<Character> chars = new ArrayList<>(size);
            for (int i = 0; i < size; i++) {
                chars.add((char) ('a' + (i % 26)));
            }
            characters = chars;
        }

        Iterable<Character> characters;
    }

    @Benchmark
    @BenchmarkMode(Throughput)
    @Warmup(batchSize = 2, iterations = 2)
    @Measurement(batchSize = 2, iterations = 3)
    public void stringJoin(Params params, Blackhole blackhole) {
        blackhole.consume(params.mode.join(params.characters));
    }

    public enum Mode {
        STREAM_APPEND {
            @Override
            String join(Iterable<Character> chars) {
                return StreamSupport.stream(chars.spliterator(), true)
                                    .collect(
                                            StringBuilder::new,
                                            StringBuilder::append,
                                            StringBuilder::append
                                    )
                                    .toString();
            }
        }, STREAM_JOIN {
            @Override
            String join(Iterable<Character> chars) {
                return StreamSupport.stream(chars.spliterator(), true)
                                    .map(Object::toString)
                                    .collect(Collectors.joining(""));
            }
        }, GUAVA_JOIN {
            @Override
            String join(Iterable<Character> chars) {
                return JOINER.join(chars);

            }
        }, ITERABLE_FOREACH {
            @Override
            String join(Iterable<Character> chars) {
                StringBuilder sb = new StringBuilder();
                chars.forEach(sb::append);
                return sb.toString();
            }
        }, JAVA7 {
            @Override
            String join(Iterable<Character> chars) {
                StringBuilder sb = new StringBuilder();
                for (Character c : chars) {
                    sb.append(c);
                }
                return sb.toString();
            }
        };

        static final Joiner JOINER = Joiner.on("");

        abstract String join(Iterable<Character> chars);

    }
}

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.stackoverflow</groupId>
    <artifactId>benchmarks-for-question-42627108</artifactId>
    <version>1.0-SNAPSHOT</version>

    <name>JMH benchmark sample: Java</name>

    <prerequisites>
        <maven>3.0</maven>
    </prerequisites>

    <dependencies>

        <dependency>
            <groupId>org.openjdk.jmh</groupId>
            <artifactId>jmh-core</artifactId>
            <version>${jmh.version}</version>
        </dependency>
        <dependency>
            <groupId>org.openjdk.jmh</groupId>
            <artifactId>jmh-samples</artifactId>
            <version>${jmh.version}</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.openjdk.jmh</groupId>
            <artifactId>jmh-generator-annprocess</artifactId>
            <version>${jmh.version}</version>
            <scope>provided</scope>
        </dependency>


        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>19.0</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.hamcrest</groupId>
            <artifactId>hamcrest-library</artifactId>
            <version>1.3</version>
            <scope>test</scope>
        </dependency>


    </dependencies>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <jmh.version>1.17.2</jmh.version>
        <javac.target>1.8</javac.target>
        <uberjar.name>benchmarks</uberjar.name>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <compilerVersion>${javac.target}</compilerVersion>
                    <source>${javac.target}</source>
                    <target>${javac.target}</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>2.2</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <finalName>${uberjar.name}</finalName>
                            <transformers>
                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>org.openjdk.jmh.Main</mainClass>
                                </transformer>
                            </transformers>
                            <filters>
                                <filter>
                                    <!--
                                        Shading signed JARs will fail without this.
                                        http://stackoverflow.com/questions/999489/invalid-signature-file-when-attempting-to-run-a-jar
                                    -->
                                    <artifact>*:*</artifact>
                                    <excludes>
                                        <exclude>META-INF/*.SF</exclude>
                                        <exclude>META-INF/*.DSA</exclude>
                                        <exclude>META-INF/*.RSA</exclude>
                                    </excludes>
                                </filter>
                            </filters>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
        <pluginManagement>
            <plugins>
                <plugin>
                    <artifactId>maven-clean-plugin</artifactId>
                    <version>2.5</version>
                </plugin>
                <plugin>
                    <artifactId>maven-deploy-plugin</artifactId>
                    <version>2.8.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-install-plugin</artifactId>
                    <version>2.5.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-jar-plugin</artifactId>
                    <version>2.4</version>
                </plugin>
                <plugin>
                    <artifactId>maven-javadoc-plugin</artifactId>
                    <version>2.9.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-resources-plugin</artifactId>
                    <version>2.6</version>
                </plugin>
                <plugin>
                    <artifactId>maven-site-plugin</artifactId>
                    <version>3.3</version>
                </plugin>
                <plugin>
                    <artifactId>maven-source-plugin</artifactId>
                    <version>2.2.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.17</version>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>

</project>