ArrayGet.java

package bench;

import org.openjdk.jmh.annotations.*;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.invoke.MutableCallSite;
import java.util.concurrent.TimeUnit;
import java.util.stream.IntStream;

@State(Scope.Benchmark)
@Warmup(iterations=5)
@Measurement(iterations=5)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Fork(1)
public class ArrayGet {
    String[] array;
    int i;
    MethodHandle mh;
    ArrayGetter dynamicGetter;

    static final MethodType mt = MethodType.methodType(String.class, String[].class, int.class);
    static final MutableCallSite mcs = new MutableCallSite(mt);
    static final MethodHandle invokerMH = mcs.dynamicInvoker();

    @Setup
    public void setup() throws Throwable {
        array = IntStream.range(0, 1000).mapToObj(String::valueOf).toArray(String[]::new);
        mh = MethodHandles.arrayElementGetter(array.getClass());
        dynamicGetter = new DynamicGetter();
        mcs.setTarget(mh);
    }

    @Benchmark
    public String arrayAccess() {
        return array[nextIndex()];
    }

    @Benchmark
    public String dynamicGetter() {
        return dynamicGetter.get(array, nextIndex());
    }

    @Benchmark
    public String methodHandle() throws Throwable {
        return (String) mh.invokeExact(array, nextIndex());
    }

    private int nextIndex() {
        if (++i >= array.length) i = 0;
        return i;
    }

    interface ArrayGetter {
        String get(String[] array, int index);
    }

    // Pretend that DynamicGetter has been dynamically generated
    static class DynamicGetter implements ArrayGetter {
        @Override
        public String get(String[] array, int index) {
            return array[index];
        }
    }

    @Benchmark
    public String dynamicMHInvoker() throws Throwable {
        return (String) invokerMH.invokeExact(array, nextIndex());
    }
}


ArrayGet.arrayAccess       avgt    5  3.431 ± 0.184  ns/op
ArrayGet.dynamicGetter     avgt    5  3.946 ± 0.132  ns/op
ArrayGet.dynamicMHInvoker  avgt    5  3.423 ± 0.271  ns/op
ArrayGet.methodHandle      avgt    5  6.926 ± 0.449  ns/op