lujiajing1126/HashMapLoadFactorBenchmark.java

## HashMapLoadFactorBenchmark.java
package com.example;

import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;
import org.openjdk.jmh.profile.GCProfiler;
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;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@State(Scope.Benchmark)
public class HashMapLoadFactorBenchmark {

    @Param({"1", "2", "3", "4", "5", "10", "15", "20"})
    public int arg;

    @Benchmark
    public void loadFactorDefault(Blackhole bh) {
        final Map<String, String> map = new HashMap<>(arg);
        for (int i = 0; i < arg; i++) {
            map.put("key" + i, "value");
        }
        bh.consume(map);
    }

    @Benchmark
    public void loadFactorOne(Blackhole bh) {
        final Map<String, String> map = new HashMap<>(arg, 1);
        for (int i = 0; i < arg; i++) {
            map.put("key" + i, "value");
        }
        bh.consume(map);
    }

    public static void main(String[] args) throws RunnerException {
        Options opt = new OptionsBuilder()
                .include(".*" + HashMapLoadFactorBenchmark.class.getSimpleName() + ".*")
                .addProfiler(GCProfiler.class)
                .build();

        new Runner(opt).run();
    }

}
	package com.example;

	import org.openjdk.jmh.annotations.*;
	import org.openjdk.jmh.infra.Blackhole;
	import org.openjdk.jmh.profile.GCProfiler;
	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;

	import java.util.HashMap;
	import java.util.Map;
	import java.util.concurrent.TimeUnit;

	@BenchmarkMode(Mode.AverageTime)
	@OutputTimeUnit(TimeUnit.NANOSECONDS)
	@Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
	@Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
	@State(Scope.Benchmark)
	public class HashMapLoadFactorBenchmark {

	@Param({"1", "2", "3", "4", "5", "10", "15", "20"})
	public int arg;

	@Benchmark
	public void loadFactorDefault(Blackhole bh) {
	final Map<String, String> map = new HashMap<>(arg);
	for (int i = 0; i < arg; i++) {
	map.put("key" + i, "value");
	}
	bh.consume(map);
	}

	@Benchmark
	public void loadFactorOne(Blackhole bh) {
	final Map<String, String> map = new HashMap<>(arg, 1);
	for (int i = 0; i < arg; i++) {
	map.put("key" + i, "value");
	}
	bh.consume(map);
	}

	public static void main(String[] args) throws RunnerException {
	Options opt = new OptionsBuilder()
	.include("." + HashMapLoadFactorBenchmark.class.getSimpleName() + ".")
	.addProfiler(GCProfiler.class)
	.build();

	new Runner(opt).run();
	}

	}