Regarding http://stackoverflow.com/a/32670178/4856258

result.txt

# JMH 1.10.3 (released 65 days ago)
# VM version: JDK 1.8.0_45, VM 25.45-b02
# VM invoker: C:\Program Files\Java\jre1.8.0_45\bin\java.exe
...
Benchmark                  (len)  Mode  Cnt      Score     Error  Units
SubstringTest.LukasEder       10  avgt   30      1.947 ±   0.012  us/op
SubstringTest.LukasEder      100  avgt   30    151.660 ±   0.524  us/op
SubstringTest.LukasEder     1000  avgt   30  52405.761 ± 183.921  us/op
SubstringTest.TagirValeev     10  avgt   30      1.712 ±   0.018  us/op
SubstringTest.TagirValeev    100  avgt   30    138.179 ±   5.063  us/op
SubstringTest.TagirValeev   1000  avgt   30  48188.499 ± 107.321  us/op

SubstringTest.java

import java.util.concurrent.TimeUnit;
import static java.util.stream.Collectors.*;
import java.util.stream.*;
import java.util.function.*;
import java.util.*;

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 SubstringTest {
  @Param({"10", "100", "1000"})
  private int len;

  private String string;

  @Setup
  public void setup() {
    string = new Random(1).ints(len, 'a', 'z'+1)
             .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append).toString();
  }

  @Benchmark
  public int LukasEder() {
    return IntStream.range(0, string.length())
             .boxed()
             .flatMap(start -> IntStream
                 .rangeClosed(start + 1, string.length())
                 .mapToObj(stop -> new AbstractMap.SimpleEntry<>(start, stop))
             )
             .map(e -> string.substring(e.getKey(), e.getValue()))
             .collect(summingInt(String::length));
  }

  @Benchmark
  public int TagirValeev() {
    return IntStream.range(0, string.length())
       .mapToObj(start -> IntStream.rangeClosed(start+1, string.length())
            .mapToObj(end -> string.substring(start, end)))
       .flatMap(Function.identity())
       .collect(summingInt(String::length));
  }
}