Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
A performance test for Collections.synchronizedMap and ConcurrentHashMap
import org.junit.Test;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
public class ConcurrentHashMapTest {
/**
* times=10^7(when times <= 10^6, their performance is very close)
* | operation n | synchronized map | ConcurrentHashMap |
* | 1 | 13173 | 5957 |
* | 2 | 11766 | 5867 |
* | 3 | 12257 | 6556 |
* | 4 | 12046 | 10483 |
* | 5 | 14612 | 8782 |
*/
@Test
public void accessPerfWithSyncMap() {
final int t = 20000000;
final Map<Integer, Integer> syncMap = Collections.synchronizedMap(new HashMap<>());
final Map<Integer, Integer> conhMap = new ConcurrentHashMap<>();
final CountDownLatch outerLatch = new CountDownLatch(2);
getMapOperationTime(t, conhMap, outerLatch);
getMapOperationTime(t, syncMap, outerLatch);
await(outerLatch);
}
/**
* read and write specific times
* @param t operation time
*/
private void getMapOperationTime(int t, Map<Integer, Integer> map, CountDownLatch outerLatch) {
run(() -> {
final CountDownLatch latch = new CountDownLatch(4);
long s = System.currentTimeMillis();
// write thread
run(() -> {
for (int i = 0; i < t; i++) {
map.put(i, i);
}
latch.countDown();
});
// read threads
run(() -> {
for (int i = 0; i < t; i++) {
map.get(i);
}
latch.countDown();
});
run(() -> {
for (int i = 0; i < t; i++) {
map.get(i);
}
latch.countDown();
});
run(() -> {
for (int i = 0; i < t; i++) {
map.get(i);
}
latch.countDown();
});
await(latch);
long e = System.currentTimeMillis();
System.out.println(map instanceof ConcurrentHashMap ?
"ConcurrentHashMap:" + (e - s) :
"synchronizedMap:" + (e - s)
);
outerLatch.countDown();
});
}
private void await(CountDownLatch latch) {
try {
latch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
private void run(Runnable r) {
new Thread(r).start();
}
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.