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验证log使用占位符相对于String 字符串的拼接可以有效提升性能。
测试代码
package com.xiaobu.JMH;import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.results.format.ResultFormatType;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.RunnerException;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.concurrent.TimeUnit;/*** @author 小布* @version 1.0.0* @className JmhLogPrint.java* @createTime 2021年09月22日 14:00:00*/
@BenchmarkMode(Mode.AverageTime) // 测试完成时间
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Warmup(iterations = 2, time = 1, timeUnit = TimeUnit.SECONDS) // 预热 2 轮,每次 1s
@Measurement(iterations = 5, time = 3, timeUnit = TimeUnit.SECONDS) // 测试 5 轮,每次 3s
@Fork(1) // fork 1 个线程
@State(Scope.Thread) // 每个测试线程一个实例
@RestController
@RequestMapping("/log")
public class JmhLogPrint {private final Logger log = LoggerFactory.getLogger(JmhLogPrint.class);public static void main(String[] args) throws RunnerException {//1、启动基准测试:输出json结果文件(用于查看可视化图)Options opt = new OptionsBuilder().include(JmhLogPrint.class.getSimpleName()) //要导入的测试类.result("D:\\JmhLogPrint.json") //输出测试结果的json文件.resultFormat(ResultFormatType.JSON)//格式化json文件.build();//2、执行测试new Runner(opt).run();}@Benchmarkpublic void appendLogPrint() {StringBuilder sb = new StringBuilder();sb.append("Hello, ");sb.append("Java");sb.append(".");sb.append("Hello, ");sb.append("Redis");sb.append(".");sb.append("Hello, ");sb.append("MySQL");sb.append(".");log.info(sb.toString());}@Benchmarkpublic void logPrintWithPlaceholder() {log.info("Hello, {}.Hello, {}.Hello, {}.", "Java", "Redis", "MySQL");}
}
结果
Benchmark Mode Cnt Score Error Units
JMH.JmhLogPrint.appendLogPrint avgt 5 274846.463 ± 1204824.140 ns/op
JMH.JmhLogPrint.logPrintWithPlaceholder avgt 5 51898.637 ± 9793.767 ns/op
直接使用 StringBuilder 拼接的方式显然要比使用占位符的方式性能要低
将json文件可视化工具
JMH Visualizer:https://jmh.morethan.io/
JMH Visual Chart:http://deepoove.com/jmh-visual-chart/
String、StringBuilder及StringBuffer的JMH基准单元测试方法:
测试代码
package com.xiaobu.JMH;import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;
import org.openjdk.jmh.results.format.ResultFormatType;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.RunnerException;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;import java.util.concurrent.TimeUnit;/*** @author 小布* @version 1.0.0* @className StringAppendJmhTest.java* @createTime 2021年09月22日 13:29:00*/
@BenchmarkMode(Mode.AverageTime) // 测试完成时间
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Warmup(iterations = 2, time = 1, timeUnit = TimeUnit.SECONDS) // 预热 2 轮,每次 1s
@Measurement(iterations = 5, time = 3, timeUnit = TimeUnit.SECONDS) // 测试 5 轮,每次 3s
@Fork(3) //Fork出3个线程来测试
@State(Scope.Thread) // 每个测试线程分配1个实例
public class StringAppendJmhTest {@Param({"2", "10", "100", "1000"})private int count; //指定添加元素的不同个数,便于分析结果public static void main(String[] args) throws RunnerException {//1、启动基准测试:输出普通文件
// Options opt = new OptionsBuilder()
// .include(ArrayAndLinkedJmhTest.class.getSimpleName()) //要导入的测试类
// .output("C:\\Users\\Administrator\\Desktop\\StringAppendJmhTest.log") //输出测试结果的普通txt文件
// .build();//1、启动基准测试:输出json结果文件(用于查看可视化图)Options opt = new OptionsBuilder().include(StringAppendJmhTest.class.getSimpleName()) //要导入的测试类.result("D:\\StringAppendJmhTest.json") //输出测试结果的json文件.resultFormat(ResultFormatType.JSON)//格式化json文件.build();//2、执行测试new Runner(opt).run();}@Setup(Level.Trial) // 初始化方法,在全部Benchmark运行之前进行public void init() {System.out.println("Start...");}@Benchmarkpublic void stringAppendTest(Blackhole blackhole) {String str = "";for (int i = 0; i < count; i++) {str = str + "Justin";}blackhole.consume(str);}@Benchmarkpublic void stringBufferAppendTest(Blackhole blackhole) {StringBuffer strBuffer = new StringBuffer();for (int i = 0; i < count; i++) {strBuffer.append("Justin");}blackhole.consume(strBuffer);}@Benchmarkpublic void stringBuilderAppendTest(Blackhole blackhole) {StringBuilder strBuilder = new StringBuilder();for (int i = 0; i < count; i++) {strBuilder.append("Justin");}blackhole.consume(strBuilder);}@TearDown(Level.Trial) // 结束方法,在全部Benchmark运行之后进行public void clear() {System.out.println("End...");}}
测试结果:
字符串拼接性能:StringBuilder > StringBuffer > String
Benchmark (count) Mode Cnt Score Error Units
JMH.StringAppendJmhTest.stringAppendTest 2 avgt 15 39.152 ± 40.463 ns/op
JMH.StringAppendJmhTest.stringAppendTest 10 avgt 15 139.626 ± 1.233 ns/op
JMH.StringAppendJmhTest.stringAppendTest 100 avgt 15 8031.421 ± 276.464 ns/op
JMH.StringAppendJmhTest.stringAppendTest 1000 avgt 15 712191.266 ± 5927.205 ns/op
JMH.StringAppendJmhTest.stringBufferAppendTest 2 avgt 15 21.510 ± 9.480 ns/op
JMH.StringAppendJmhTest.stringBufferAppendTest 10 avgt 15 166.773 ± 274.604 ns/op
JMH.StringAppendJmhTest.stringBufferAppendTest 100 avgt 15 1159.299 ± 103.268 ns/op
JMH.StringAppendJmhTest.stringBufferAppendTest 1000 avgt 15 10173.023 ± 1148.979 ns/op
JMH.StringAppendJmhTest.stringBuilderAppendTest 2 avgt 15 16.613 ± 0.347 ns/op
JMH.StringAppendJmhTest.stringBuilderAppendTest 10 avgt 15 89.340 ± 0.731 ns/op
JMH.StringAppendJmhTest.stringBuilderAppendTest 100 avgt 15 1029.786 ± 11.204 ns/op
JMH.StringAppendJmhTest.stringBuilderAppendTest 1000 avgt 15 9151.069 ± 126.842 ns/op
Commons Lang StringUtils.replace performance vs String.replace
测试代码
package com.xiaobu.JMH;import org.apache.commons.lang3.StringUtils;
import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.RunnerException;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;import java.util.concurrent.TimeUnit;/*** @author 小布* @version 1.0.0* @className StringReplaceBenchmark.java* @createTime 2021年09月22日 14:24:00*/
@BenchmarkMode(Mode.AverageTime) // 测试完成时间
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Warmup(iterations = 2, time = 1, timeUnit = TimeUnit.SECONDS) // 预热 2 轮,每次 1s
@Measurement(iterations = 5, time = 3, timeUnit = TimeUnit.SECONDS) // 测试 5 轮,每次 3s
@Fork(1) // fork 1 个线程
@State(Scope.Thread) // 每个测试线程一个实例
public class StringReplaceBenchmark {private static final String SHORT_STRING_NO_MATCH = "ABC";private static final String SHORT_STRING_ONE_MATCH = "a'BC";private static final String SHORT_STRING_SEVERAL_MATCHES = "'a'b'c'";private static final String LONG_STRING_NO_MATCH ="ABCABCABCABCABCABCABCABCABCABCABCABCABCABCABCABCABCABCABCABCABCABCABCABC";private static final String LONG_STRING_ONE_MATCH ="ABCABCABCABCABCABCABCABCABCABCABCa'BCABCABCABCABCABCABCABCABCABCABCABCABC";private static final String LONG_STRING_SEVERAL_MATCHES ="ABCABCa'BCABCABCABCABCABC'ABCABCABCa'BCABCABCABCABCABCa'BCABCABCABCABCABCABC";public static void main(String[] args) throws RunnerException {Options options = new OptionsBuilder().include(StringReplaceBenchmark.class.getSimpleName()).build();new Runner(options).run();}@Benchmarkpublic void shortStringNoMatch(Blackhole blackhole) {blackhole.consume(SHORT_STRING_NO_MATCH.replace("'", "''"));}@Benchmarkpublic void shortStringNoMatchUtils(Blackhole blackhole) {blackhole.consume(StringUtils.replace(SHORT_STRING_NO_MATCH, "'", "''"));}@Benchmarkpublic void longStringNoMatch(Blackhole blackhole) {blackhole.consume(LONG_STRING_NO_MATCH.replace("'", "''"));}@Benchmarkpublic void longStringNoMatchUtils(Blackhole blackhole) {blackhole.consume(StringUtils.replace(LONG_STRING_NO_MATCH, "'", "''"));}@Benchmarkpublic void shortString1Match(Blackhole blackhole) {blackhole.consume(SHORT_STRING_ONE_MATCH.replace("'", "''"));}@Benchmarkpublic void shortString1MatchUtils(Blackhole blackhole) {blackhole.consume(StringUtils.replace(SHORT_STRING_ONE_MATCH, "'", "''"));}@Benchmarkpublic void longString1Match(Blackhole blackhole) {blackhole.consume(LONG_STRING_ONE_MATCH.replace("'", "''"));}@Benchmarkpublic void longString1MatchUtils(Blackhole blackhole) {blackhole.consume(StringUtils.replace(LONG_STRING_ONE_MATCH, "'", "''"));}@Benchmarkpublic void shortStringNMatch(Blackhole blackhole) {blackhole.consume(SHORT_STRING_SEVERAL_MATCHES.replace("'", "''"));}@Benchmarkpublic void shortStringNMatchUtils(Blackhole blackhole) {blackhole.consume(StringUtils.replace(SHORT_STRING_SEVERAL_MATCHES, "'", "''"));}@Benchmarkpublic void longStringNMatch(Blackhole blackhole) {blackhole.consume(LONG_STRING_SEVERAL_MATCHES.replace("'", "''"));}@Benchmarkpublic void longStringNMatchUtils(Blackhole blackhole) {blackhole.consume(StringUtils.replace(LONG_STRING_SEVERAL_MATCHES, "'", "''"));}
}
测试结果:
Benchmark Mode Cnt Score Error Units
JMH.StringReplaceBenchmark.longString1Match avgt 5 1542.101 ± 8069.146 ns/op
JMH.StringReplaceBenchmark.longString1MatchUtils avgt 5 408.031 ± 1984.070 ns/op
JMH.StringReplaceBenchmark.longStringNMatch avgt 5 790.396 ± 1068.888 ns/op
JMH.StringReplaceBenchmark.longStringNMatchUtils avgt 5 310.045 ± 815.440 ns/op
JMH.StringReplaceBenchmark.longStringNoMatch avgt 5 172.684 ± 322.380 ns/op
JMH.StringReplaceBenchmark.longStringNoMatchUtils avgt 5 21.944 ± 0.323 ns/op
JMH.StringReplaceBenchmark.shortString1Match avgt 5 160.640 ± 2.932 ns/op
JMH.StringReplaceBenchmark.shortString1MatchUtils avgt 5 89.461 ± 340.988 ns/op
JMH.StringReplaceBenchmark.shortStringNMatch avgt 5 296.488 ± 56.479 ns/op
JMH.StringReplaceBenchmark.shortStringNMatchUtils avgt 5 71.800 ± 12.094 ns/op
JMH.StringReplaceBenchmark.shortStringNoMatch avgt 5 97.064 ± 26.855 ns/op
JMH.StringReplaceBenchmark.shortStringNoMatchUtils avgt 5 5.018 ± 0.910 ns/opProcess finished with exit code 0
字符串replace性能:Commons Lang StringUtils.replace > String.replace(java8)
在现代 Java 中(JDK>1.8),情况不再如此。String.replace在Java-9 中从正则表达式到 StringBuilder 进行了改进,在Java-13 中进行了更多改进,以直接分配目标byte[]数组提前计算其确切大小。由于使用了内部 JDK 特性,例如分配未初始化数组的能力、访问 String 编码器的能力以及使用String避免复制的私有构造函数的能力,当前实现不太可能被第三方实现击败。
参考:
Java–☀️面试官:讲一下String、StringBuilder及StringBuffer区别?❤️【⭐初学者面试必备⭐】
为什么要用JMH?何时应该用?
Commons Lang StringUtils.replace performance vs String.replace
JMH-大厂是如何使用JMH进行Java代码性能测试的?必须掌握!
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