ConcurrentHashMap vs. HashMap performance

benchmark.txt

Benchmark        (size)  Mode  Cnt   Score   Error  Units
MapBench.chmGet    1024  avgt    5  20,363 ± 0,976  ns/op
MapBench.hmGet     1024  avgt    5  20,661 ± 0,898  ns/op

MapBench.java

package bench;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Param;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ThreadLocalRandom;

@State(Scope.Benchmark)
public class MapBench {

    @Param({"1024"})
    private int size;

    private String[] keys;

    private final Map<String, String> chm = new ConcurrentHashMap<>();
    private final Map<String, String> hm = new HashMap<>();

    @Setup
    public void setup() {
        keys = new String[size];
        for (int i = 0; i < size; i++) {
            keys[i] = "key" + i;
            hm.put(keys[i], "value" + i);
            chm.put(keys[i], "value" + i);
        }
    }
    
    private String randomKey() {
        return keys[ThreadLocalRandom.current().nextInt(keys.length)];
    }

    @Benchmark
    public String chmGet() {
        return chm.get(randomKey()); 
    }

    @Benchmark
    public String hmGet() {
        return hm.get(randomKey());
    }
}