Stream API benchmark

Concat.java

import java.util.*;
import java.util.function.*;
import java.util.stream.*;

import java.util.concurrent.TimeUnit;

import org.openjdk.jmh.annotations.*;
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;

@BenchmarkMode(Mode.AverageTime)
@Fork(3)
@State(Scope.Benchmark)
@OutputTimeUnit(TimeUnit.MICROSECONDS)
@Warmup(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@Measurement(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
public class Concat {
  @Param({"10", "1000", "100000"})
  private int n;

  @Param({"true", "false"})
  private boolean pollute;

  private List<String> input;

  @Setup
  public void setup() {
    input = Stream.generate(() -> new String("abcdef")).limit(n).collect(Collectors.toList());
    if(pollute) {
      for(int i=0; i<1000; i++) {
        input.stream().map(s -> s+"1").collect(Collectors.toList());
        input.stream().map(s -> s+"2").collect(Collectors.toList());
        input.stream().map(s -> s+"3").collect(Collectors.toList());
      }
    }
  }

  @Benchmark
  public List<String> plain() {
    List<String> result = new ArrayList<>();
    for(String s : input) result.add(s+"xyz");
    return result;
  }

  @Benchmark
  public List<String> stream() {
    return input.stream().map(s -> s+"xyz").collect(Collectors.toList());
  }
}

result.txt

# JMH 1.13 (released 27 days ago)
# VM version: JDK 1.8.0_91, VM 25.91-b14
# VM invoker: C:\Program Files\Java\jre1.8.0_91\bin\java.exe
Benchmark         (n)  (pollute)  Mode  Cnt     Score     Error  Units
Concat.stream      10       true  avgt   15     0,335 ±   0,008  us/op
Concat.stream      10      false  avgt   15     0,312 ±   0,006  us/op
Concat.stream    1000       true  avgt   15    26,733 ±   0,740  us/op
Concat.stream    1000      false  avgt   15    24,910 ±   0,477  us/op
Concat.stream  100000       true  avgt   15  3127,121 ± 299,316  us/op
Concat.stream  100000      false  avgt   15  2869,882 ±  86,572  us/op
Concat.plain       10       true  avgt   15     0,254 ±   0,011  us/op
Concat.plain       10      false  avgt   15     0,258 ±   0,013  us/op
Concat.plain     1000       true  avgt   15    25,366 ±   0,438  us/op
Concat.plain     1000      false  avgt   15    24,992 ±   0,705  us/op
Concat.plain   100000       true  avgt   15  2829,553 ± 162,468  us/op
Concat.plain   100000      false  avgt   15  2762,287 ± 122,223  us/op