.collect(
                                    Collectors.toMap(
                                            word -> word,
                                            word -> 1,
                                            (count1, count2) -> count1 + count2
                                    )
                            )

  .collect(groupingBy(identity(),counting()))  // identity() === t->t
  .forEach((k, v) -> System.out.println(k +" : " + v));

import java.util.concurrent.TimeUnit;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Warmup;
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;

@Warmup(iterations = 3)
@Measurement(iterations = 10)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@State(Scope.Benchmark)
public class MicroTest {

    public interface Foo {

        public Object foor();
    }

    @Benchmark
    public Foo inner() {
        return new Foo() {

            @Override
            public Object foor() {
                return "42";
            }
        };
    }
    
    @Benchmark
    public Foo lambda() {
        return () -> "42";
    }
    
    public static void main(String[] args) throws RunnerException {
        
        Options opt = new OptionsBuilder()
                .include(MicroTest.class.getSimpleName())
                .forks(1)
                .build();

        new Runner(opt).run();
    }

}

# Run complete. Total time: 00:00:27

Benchmark         Mode  Cnt  Score   Error  Units
MicroTest.inner   avgt   10  6,419 ± 1,052  ns/op
MicroTest.lambda  avgt   10  2,855 ± 0,065  ns/op

$ javap -c MicroTest.class 
Compiled from "MicroTest.java"
public class ru.isalnikov.benchmarkfactorial.MicroTest {
  public ru.isalnikov.benchmarkfactorial.MicroTest();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: return

  public ru.isalnikov.benchmarkfactorial.MicroTest$Foo inner();
    Code:
       0: new           #2                  // class ru/isalnikov/benchmarkfactorial/MicroTest$1
       3: dup
       4: aload_0
       5: invokespecial #3                  // Method ru/isalnikov/benchmarkfactorial/MicroTest$1."<init>":(Lru/isalnikov/benchmarkfactorial/MicroTest;)V
       8: areturn

  public ru.isalnikov.benchmarkfactorial.MicroTest$Foo lambda();
    Code:
       0: invokedynamic #4,  0              // InvokeDynamic #0:foor:()Lru/isalnikov/benchmarkfactorial/MicroTest$Foo;
       5: areturn

  public static void main(java.lang.String[]) throws org.openjdk.jmh.runner.RunnerException;
    Code:
       0: new           #5                  // class org/openjdk/jmh/runner/options/OptionsBuilder
       3: dup
       4: invokespecial #6                  // Method org/openjdk/jmh/runner/options/OptionsBuilder."<init>":()V
       7: ldc           #7                  // class ru/isalnikov/benchmarkfactorial/MicroTest
       9: invokevirtual #8                  // Method java/lang/Class.getSimpleName:()Ljava/lang/String;
      12: invokevirtual #9                  // Method org/openjdk/jmh/runner/options/OptionsBuilder.include:(Ljava/lang/String;)Lorg/openjdk/jmh/runner/options/ChainedOptionsBuilder;
      15: iconst_1
      16: invokeinterface #10,  2           // InterfaceMethod org/openjdk/jmh/runner/options/ChainedOptionsBuilder.forks:(I)Lorg/openjdk/jmh/runner/options/ChainedOptionsBuilder;
      21: invokeinterface #11,  1           // InterfaceMethod org/openjdk/jmh/runner/options/ChainedOptionsBuilder.build:()Lorg/openjdk/jmh/runner/options/Options;
      26: astore_1
      27: new           #12                 // class org/openjdk/jmh/runner/Runner
      30: dup
      31: aload_1
      32: invokespecial #13                 // Method org/openjdk/jmh/runner/Runner."<init>":(Lorg/openjdk/jmh/runner/options/Options;)V
      35: invokevirtual #14                 // Method org/openjdk/jmh/runner/Runner.run:()Ljava/util/Collection;
      38: pop
      39: return
}

    private Foo cached = new Foo() {

        @Override
        public Object foor() {
            return "42";
        }
    };
    
    @Benchmark
    public Foo inner_cache() {
        return cached;
    }

Benchmark              Mode  Cnt  Score   Error  Units
MicroTest.inner        avgt   10  6,395 ± 0,501  ns/op
MicroTest.inner_cache  avgt   10  3,915 ± 0,721  ns/op
MicroTest.lambda       avgt   10  3,330 ± 0,744  ns/op