// understandingcollections/jmh/Maps.java

// (c)2016 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://mindviewinc.com/Books/OnJava/ for more book information.

// Performance differences between Maps

package understandingcollections.jmh;

import org.openjdk.jmh.annotations.*;

import org.openjdk.jmh.infra.Blackhole;

import java.util.*;

import static java.util.concurrent.TimeUnit.*;

@State(Scope.Thread)

@Warmup(iterations = 5, time = 1, timeUnit = SECONDS)

@Measurement(iterations = 5, time = 1, timeUnit = SECONDS)

@Fork(1)

@BenchmarkMode(Mode.AverageTime)

@OutputTimeUnit(MICROSECONDS)

public class Maps {

private Map<Integer, Integer> map;

@Param({"HashMap", "TreeMap", "LinkedHashMap",

"IdentityHashMap", "WeakHashMap", "Hashtable",})

private String type;

private int begin;

private int end;

@Setup

public void setup() {

switch(type) {

case "HashMap":

map = new HashMap<>();

break;

case "TreeMap":

map = new TreeMap<>();

break;

case "LinkedHashMap":

map = new LinkedHashMap<>();

break;

case "IdentityHashMap":

map = new IdentityHashMap<>();

break;

case "WeakHashMap":

map = new WeakHashMap<>();

break;

case "Hashtable":

map = new Hashtable<>();

break;

default:

throw new IllegalStateException("Unknown " + type);

}

begin = 1;

end = 256;

for (int i = begin; i < end; i++) {

map.put(i, i);

}

}

@Benchmark

public void get(Blackhole bh) {

for (int i = begin; i < end; i++) {

bh.consume(map.get(i));

}

}

@Benchmark

public void put() {

for (int i = begin; i < end; i++) {

map.put(i, i);

}

}

@Benchmark

public void iterate(Blackhole bh) {

Iterator it = map.entrySet().iterator();

while(it.hasNext())

bh.consume(it.next());

}

}