<span style="font-size:18px;">package JUC;
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。
*
*
*
*/
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--;
}
}
}
</span>
运行结果：
Put time HashMapSync=1839ms. Put time ConcurrentHashMap=1623ms. Put time Hashtable=2067ms. Get time HashMapSync=1649ms. Get time ConcurrentHashMap=1373ms. Get time Hashtable=1820ms.
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