Re https://habrahabr.ru/post/262139/

HeadTailTest.java

package test;

import java.util.concurrent.TimeUnit;
import one.util.streamex.*;
import java.util.stream.*;
import java.util.function.*;
import java.util.*;
import java.math.*;

import org.openjdk.jmh.infra.Blackhole;
import org.openjdk.jmh.annotations.*;
 
@Warmup(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@Measurement(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.MICROSECONDS)
@Fork(3)
@State(Scope.Benchmark)
public class HeadTailTest {
  public static <T, R> StreamEx<R> map(StreamEx<T> input, Function<T, R> mapper) {
    return input.headTail((head, tail) -> map(tail, mapper).prepend(mapper.apply(head)));
  }  

  List<String> input;

  @Setup
  public void setup() {
    input = new Random(1).doubles(10000).mapToObj(String::valueOf).collect(Collectors.toList());
  }

  @Benchmark
  public int jdkSimple() {
    return input.stream().map(x -> x).collect(Collectors.summingInt(String::length));
  }

  @Benchmark
  public List<String> jdkComplex() {
    return input.stream().map(x -> x.replaceAll("[123]", "")).collect(Collectors.toList());
  }

  @Benchmark
  public int htSimple() {
    return map(StreamEx.of(input), x -> x).collect(Collectors.summingInt(String::length));
  }

  @Benchmark
  public List<String> htComplex() {
    return map(StreamEx.of(input), x -> x.replaceAll("[123]", "")).collect(Collectors.toList());
  }
}