Java中的HashMap和ConcurrentHashMap的并发性能测试

先看看代码吧，模拟1000个并发，每个测试1000次操作，循环测试10轮。分别测试Put和Get操作import java.util.Collections;

import java.util.HashMap;
import java.util.Hashtable;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
 * 测试HashMap和ConcurrentHashMap的并发性能差别。
 *
 * @author 老紫竹 JAVA世纪网(java2000.net)
 *
 */
public class T {
  static final int threads = 1000;
  static final int NUMBER = 1000;
  public static void main(String[] args) throws Exception {
    Map<String, Integer> hashmapSync = Collections
        .synchronizedMap(new HashMap<String, Integer>());
    Map<String, Integer> concurrentHashMap = new ConcurrentHashMap<String, Integer>();
    Map<String, Integer> hashtable = new Hashtable<String, Integer>();
    long totalA = 0;
    long totalB = 0;
    long totalC = 0;
    for (int i = 0; i <= 10; i++) {
      totalA += testPut(hashmapSync);
      totalB += testPut(concurrentHashMap);
      totalC += testPut(hashtable);
    }
    System.out.println("Put time HashMapSync=" + totalA + "ms.");
    System.out.println("Put time ConcurrentHashMap=" + totalB + "ms.");
    System.out.println("Put time Hashtable=" + totalC + "ms.");
    totalA = 0;
    totalB = 0;
    totalC = 0;
    for (int i = 0; i <= 10; i++) {
      totalA += testGet(hashmapSync);
      totalB += testGet(concurrentHashMap);
      totalC += testGet(hashtable);
    }
    System.out.println("Get time HashMapSync=" + totalA + "ms.");
    System.out.println("Get time ConcurrentHashMap=" + totalB + "ms.");
    System.out.println("Get time Hashtable=" + totalC + "ms.");
  }
  public static long testPut(Map<String, Integer> map) throws Exception {
    long start = System.currentTimeMillis();
    for (int i = 0; i < threads; i++) {
      new MapPutThread(map).start();
    }
    while (MapPutThread.counter > 0) {
      Thread.sleep(1);
    }
    return System.currentTimeMillis() - start;
  }
  public static long testGet(Map<String, Integer> map) throws Exception {
    long start = System.currentTimeMillis();
    for (int i = 0; i < threads; i++) {
      new MapPutThread(map).start();
    }
    while (MapPutThread.counter > 0) {
      Thread.sleep(1);
    }
    return System.currentTimeMillis() - start;
  }
}
class MapPutThread extends Thread {
  static int counter = 0;
  static Object lock = new Object();
  private Map<String, Integer> map;
  private String key = this.getId() + "";
  MapPutThread(Map<String, Integer> map) {
    synchronized (lock) {
      counter++;
    }
    this.map = map;
  }
  public void run() {
    for (int i = 1; i <= T.NUMBER; i++) {
      map.put(key, i);
    }
    synchronized (lock) {
      counter--;
    }
  }
}
class MapGetThread extends Thread {
  static int counter = 0;
  static Object lock = new Object();
  private Map<String, Integer> map;
  private String key = this.getId() + "";
  MapGetThread(Map<String, Integer> map) {
    synchronized (lock) {
      counter++;
    }
    this.map = map;
  }
  public void run() {
    for (int i = 1; i <= T.NUMBER; i++) {
      map.get(key);
    }
    synchronized (lock) {
      counter--;
    }
  }
}

运行结果
Put time HashMapSync=3966ms.
Put time ConcurrentHashMap=1892ms.
Put time Hashtable=3892ms.
Get time HashMapSync=3812ms.
Get time ConcurrentHashMap=1828ms.
Get time Hashtable=3985ms.

结论
ConcurrentHashMap的性能比同步的HashMap快一倍左右，同步的HashMap和Hashtable的性能相当。

原帖地址：http://www.java2000.net/p12427