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JMH ?????? Java ??????????? Java ???????? Oracle ?????? JIT???????? JVM?Java ???????????????????????

?????????? JMH ?? StringBuilder.append() ???????????????????

1. ????

????????? JMH ???????? Maven ????????????? JMH ????????????????

       
    
     org.openjdk.jmh
        
    
     jmh-core
        
    
     1.23
    
   
       
    
     org.openjdk.jmh
        
    
     jmh-generator-annprocess
        
    
     1.23
    
   

2. ?????

???????????? Java ? StringConnectTest?????????????????????????

public class StringConnectTest {    @Param(value = {"10", "50", "100"})    private int length;    @Benchmark    public void testStringBuilderAdd(Blackhole blackhole) {        StringBuilder sb = new StringBuilder();        for (int i = 0; i < length; i++) {            sb.append(i);        }        blackhole.consume(sb.toString());    }    @Benchmark    public void testStringAdd(Blackhole blackhole) {        String a = "";        for (int i = 0; i < length; i++) {            a += i;        }        blackhole.consume(a);    }    public static void main(String[] args) throws RunnerException {        Options opt = new OptionsBuilder()                .include(StringConnectTest.class.getSimpleName())                .result("result.json")                .resultFormat(ResultFormatType.JSON)                .build();        new Runner(opt).run();    }}

3. ??????

? main ???????? OptionsBuilder ?????????????????????

public static void main(String[] args) throws RunnerException {    Options opt = new OptionsBuilder()            .include(StringConnectTest.class.getSimpleName())            .result("result.json")            .resultFormat(ResultFormatType.JSON)            .build();    new Runner(opt).run();}

4. ??????

?? Maven ???????????????????????

mvn clean install -Djmh_demo=true StringConnectTest

5. ??????

????????????? JSON ??????? result.json??????????????????????????????????????

6. ??????

??????????????? StringBuilder.append() ???? String ????????????????????

???????????????? StringBuilder.append() ????????

7. ?? JMH ???

JMH ??????????????????????????????????????????????

• @Benchmark ??????????????
• @Param ????????????
• @State ????????????
• @Warmup ? @Measurement ??????????????????
• @Fork ???????????????

8. JMH ????

????????? JMH ????????? Maven ??????????????? Maven ???????

       
            
     
      org.apache.maven.plugins
             
     
      maven-shade-plugin
             
     
      2.4.1
             
                 
                      
       
        package
                       
                           
        
         shade
                        
                       
                           
        
         jmh-demo
                            
         
          
          
           org.openjdk.jmh.Main
           
          
                        
                   
              
         
    
   

9. ?? JMH Visual Chart

??????????????????? JMH Visual Chart ???????????

10. ?????????

??? JMH ???????????????????????

• ???????????
• ???????????

????????????????

• ???????????????
• ???????????
• ?????????????

???????????????? JMH ??????????????????????????