JMH Java准测试工具套件

什么是JMH

官网

http://openjdk.java.net/projects/code-tools/jmh/

创建JMH测试

创建Maven项目，添加依赖

<?xml version="1.0" encoding="UTF-8"?>
<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>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <encoding>UTF-8</encoding>
        <java.version>1.8</java.version>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <groupId>zhangxueliang.com</groupId>
    <artifactId>HelloJMH2</artifactId>
    <version>1.0-SNAPSHOT</version>


    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.openjdk.jmh/jmh-core -->
        <dependency>
            <groupId>org.openjdk.jmh</groupId>
            <artifactId>jmh-core</artifactId>
            <version>1.21</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.openjdk.jmh/jmh-generator-annprocess -->
        <dependency>
            <groupId>org.openjdk.jmh</groupId>
            <artifactId>jmh-generator-annprocess</artifactId>
            <version>1.21</version>
            <scope>test</scope>
        </dependency>
    </dependencies>


</project>

idea安装JMH插件 JMH plugin v1.0.3
由于用到了注解，打开运行程序注解配置

compiler -> Annotation Processors -> Enable Annotation Processing

定义需要测试类PS (ParallelStream)

package com.zhangxueliang.jmh;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class PS {

	static List<Integer> nums = new ArrayList<>();
	static {
		Random r = new Random();
		for (int i = 0; i < 10000; i++) nums.add(1000000 + r.nextInt(1000000));
	}

	static void foreach() {
		nums.forEach(v->isPrime(v));
	}

	static void parallel() {
		nums.parallelStream().forEach(PS::isPrime);
	}
	
	static boolean isPrime(int num) {
		for(int i=2; i<=num/2; i++) {
			if(num % i == 0) return false;
		}
		return true;
	}
}

写单元测试

这个测试类一定要在test package下面

运行测试类，如果遇到下面的错误：

ERROR: org.openjdk.jmh.runner.RunnerException: ERROR: Exception while trying to acquire the JMH lock (C:\WINDOWS\/jmh.lock): C:\WINDOWS\jmh.lock (拒绝访问。), exiting. Use -Djmh.ignoreLock=true to forcefully continue.
	at org.openjdk.jmh.runner.Runner.run(Runner.java:216)
	at org.openjdk.jmh.Main.main(Main.java:71)