Quick JMH test for https://dzone.com/articles/creating-maps-with-named-lambdas. Licensed under Apache 2.0 [ https://www.apache.org/licenses/LICENSE-2.0 ]

_result.txt

# JMH 1.13 (released 139 days ago)
# VM version: JDK 1.8.0_101, VM 25.101-b13
# VM invoker: C:\Program Files\Java\jdk1.8.0_101\jre\bin\java.exe
# VM options: <none>
Benchmark          Mode  Cnt      Score     Error  Units
MapTest.fancy      avgt   15  42821,529 ± 425,169  ns/op
MapTest.oldSchool  avgt   15    182,887 ±   2,666  ns/op

MapTest.java

import org.openjdk.jmh.annotations.*;

import java.io.Serializable;
import java.lang.invoke.SerializedLambda;
import java.lang.reflect.Method;
import java.util.*;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;

@BenchmarkMode(Mode.AverageTime)
@Warmup(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@Measurement(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Fork(3)
@State(Scope.Benchmark)
public class MapTest {
    public interface KeyValueStringFunction<T> extends Function<String, T>, Serializable {
        default String key() {
            return functionalMethod().getParameters()[0].getName();
        }
        default T value() {
            return apply(key());
        }
        default Method functionalMethod() {
            final SerializedLambda serialzedLabmda = serializedLambda();
            final Class<?> implementationClass = implementationClass(serialzedLabmda);
            return Stream.of(implementationClass.getDeclaredMethods())
                         .filter(m -> Objects.equals(m.getName(), serialzedLabmda.getImplMethodName()))
                         .findFirst()
                         .orElseThrow(RuntimeException::new);
        }
        default Class<?> implementationClass(SerializedLambda serializedLambda) {
            try {
                final String className = serializedLambda.getImplClass().replaceAll("/", ".");
                return Class.forName(className);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
        default SerializedLambda serializedLambda() {
            try {
                final Method replaceMethod = getClass().getDeclaredMethod("writeReplace");
                replaceMethod.setAccessible(true);
                return (SerializedLambda) replaceMethod.invoke(this);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
        @SafeVarargs
        static <V> Map<String, V> mapOf(KeyValueStringFunction<V>... mappings) {
            return Stream.of(mappings)
                         .collect(
                                 Collectors.toMap(
                                         KeyValueStringFunction::key,
                                         KeyValueStringFunction::value
                                 )
                         );
        }
    }

    public static class Maps {
        public static <K, V> Map<K, V> of(K k1, V v1) {
            return Collections.singletonMap(k1, v1);
        }

        public static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2) {
            Map<K, V> map = new HashMap<>();
            map.put(k1, v1);
            map.put(k2, v2);
            return map;
        }

        public static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {
            Map<K, V> map = new HashMap<>();
            map.put(k1, v1);
            map.put(k2, v2);
            map.put(k3, v3);
            return map;
        }

        public static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
            Map<K, V> map = new HashMap<>();
            map.put(k1, v1);
            map.put(k2, v2);
            map.put(k3, v3);
            map.put(k4, v4);
            return map;
        }

        public static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
            Map<K, V> map = new HashMap<>();
            map.put(k1, v1);
            map.put(k2, v2);
            map.put(k3, v3);
            map.put(k4, v4);
            map.put(k5, v5);
            return map;
        }
        // continue if you're like
    }

    @Benchmark
    public Map<String, Map<String, Integer>> fancy() {
        return KeyValueStringFunction.mapOf(
                usa -> KeyValueStringFunction.mapOf(
                        new_york    -> 8_550_405,
                        los_angeles -> 3_971_883,
                        chicago     -> 2_720_546
                ),
                canada -> KeyValueStringFunction.mapOf(
                        toronto  -> 2_615_060,
                        montreal -> 1_649_519,
                        calgary  -> 1_096_833
                )
        );
    }

    @Benchmark
    public Map<String, Map<String, Integer>> oldSchool() {
        return Maps.of(
                "usa" , Maps.of(
                        "new_york"    , 8_550_405,
                        "los_angeles" , 3_971_883,
                        "chicago"     , 2_720_546
                ),
                "canada" , Maps.of(
                        "toronto"  , 2_615_060,
                        "montreal" , 1_649_519,
                        "calgary"  , 1_096_833
                )
        );
    }
}

output.txt

# JMH 1.13 (released 139 days ago)
# VM version: JDK 1.8.0_101, VM 25.101-b13
# VM invoker: C:\Program Files\Java\jdk1.8.0_101\jre\bin\java.exe
# VM options: <none>
# Warmup: 5 iterations, 500 ms each
# Measurement: 5 iterations, 500 ms each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Average time, time/op
# Benchmark: com.example.MapTest.fancy

# Run progress: 0,00% complete, ETA 00:00:30
# Fork: 1 of 3
# Warmup Iteration   1: 64180,734 ns/op
# Warmup Iteration   2: 43214,874 ns/op
# Warmup Iteration   3: 46478,840 ns/op
# Warmup Iteration   4: 42429,870 ns/op
# Warmup Iteration   5: 43279,656 ns/op
Iteration   1: 42796,956 ns/op
Iteration   2: 42534,985 ns/op
Iteration   3: 42400,713 ns/op
Iteration   4: 42592,634 ns/op
Iteration   5: 42338,768 ns/op

# Run progress: 16,67% complete, ETA 00:00:26
# Fork: 2 of 3
# Warmup Iteration   1: 65591,349 ns/op
# Warmup Iteration   2: 43281,099 ns/op
# Warmup Iteration   3: 43494,893 ns/op
# Warmup Iteration   4: 43583,397 ns/op
# Warmup Iteration   5: 42796,050 ns/op
Iteration   1: 43168,731 ns/op
Iteration   2: 43542,718 ns/op
Iteration   3: 42949,553 ns/op
Iteration   4: 42573,148 ns/op
Iteration   5: 42439,348 ns/op

# Run progress: 33,33% complete, ETA 00:00:21
# Fork: 3 of 3
# Warmup Iteration   1: 65814,014 ns/op
# Warmup Iteration   2: 43806,589 ns/op
# Warmup Iteration   3: 47327,194 ns/op
# Warmup Iteration   4: 43106,877 ns/op
# Warmup Iteration   5: 43630,530 ns/op
Iteration   1: 43299,582 ns/op
Iteration   2: 42397,365 ns/op
Iteration   3: 43432,398 ns/op
Iteration   4: 42926,815 ns/op
Iteration   5: 42929,221 ns/op


Result "fancy":
  42821,529 ±(99.9%) 425,169 ns/op [Average]
  (min, avg, max) = (42338,768, 42821,529, 43542,718), stdev = 397,703
  CI (99.9%): [42396,360, 43246,698] (assumes normal distribution)


# JMH 1.13 (released 139 days ago)
# VM version: JDK 1.8.0_101, VM 25.101-b13
# VM invoker: C:\Program Files\Java\jdk1.8.0_101\jre\bin\java.exe
# VM options: <none>
# Warmup: 5 iterations, 500 ms each
# Measurement: 5 iterations, 500 ms each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Average time, time/op
# Benchmark: com.example.MapTest.oldSchool

# Run progress: 50,00% complete, ETA 00:00:15
# Fork: 1 of 3
# Warmup Iteration   1: 249,428 ns/op
# Warmup Iteration   2: 243,986 ns/op
# Warmup Iteration   3: 209,563 ns/op
# Warmup Iteration   4: 284,515 ns/op
# Warmup Iteration   5: 179,470 ns/op
Iteration   1: 186,048 ns/op
Iteration   2: 183,430 ns/op
Iteration   3: 182,803 ns/op
Iteration   4: 183,313 ns/op
Iteration   5: 183,533 ns/op

# Run progress: 66,67% complete, ETA 00:00:10
# Fork: 2 of 3
# Warmup Iteration   1: 251,519 ns/op
# Warmup Iteration   2: 244,423 ns/op
# Warmup Iteration   3: 212,975 ns/op
# Warmup Iteration   4: 275,071 ns/op
# Warmup Iteration   5: 183,705 ns/op
Iteration   1: 183,017 ns/op
Iteration   2: 183,891 ns/op
Iteration   3: 184,690 ns/op
Iteration   4: 188,091 ns/op
Iteration   5: 181,658 ns/op

# Run progress: 83,33% complete, ETA 00:00:05
# Fork: 3 of 3
# Warmup Iteration   1: 250,888 ns/op
# Warmup Iteration   2: 240,091 ns/op
# Warmup Iteration   3: 206,969 ns/op
# Warmup Iteration   4: 277,986 ns/op
# Warmup Iteration   5: 182,737 ns/op
Iteration   1: 182,185 ns/op
Iteration   2: 181,019 ns/op
Iteration   3: 180,086 ns/op
Iteration   4: 177,318 ns/op
Iteration   5: 182,222 ns/op


Result "oldSchool":
  182,887 ±(99.9%) 2,666 ns/op [Average]
  (min, avg, max) = (177,318, 182,887, 188,091), stdev = 2,494
  CI (99.9%): [180,221, 185,553] (assumes normal distribution)


# Run complete. Total time: 00:00:32

Benchmark          Mode  Cnt      Score     Error  Units
MapTest.fancy      avgt   15  42821,529 ± 425,169  ns/op
MapTest.oldSchool  avgt   15    182,887 ±   2,666  ns/op