怎么证明HashMap和SynchronizedMap和ConcurrentHashMap性能优劣
代码如下：
import java.util.Collections; import java.util.HashMap; import java.util.Hashtable; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit; public class HashTableVsSynchronizedMapVsConcurrentHashMap { public final static int THREAD_POOL_SIZE = 5; public static Map<String, Integer> hashTableObject = null; public static Map<String, Integer> synchronizedMapObject = null; public static Map<String, Integer> concurrentHashMapObject = null; public static void main(String[] args) throws InterruptedException { // 测试HashTable hashTableObject = new Hashtable<String, Integer>(); performTest(hashTableObject); // 测试synchronizedMap synchronizedMapObject = Collections.synchronizedMap(new HashMap<String, Integer>()); performTest(synchronizedMapObject); // 测试ConcurrentHashMap concurrentHashMapObject = new ConcurrentHashMap<String, Integer>(); performTest(concurrentHashMapObject); } private static void performTest(final Map<String, Integer> map) throws InterruptedException { System.err.println("开始测试 : " + map.getClass()); long averageTime = 0; for (int i = 0; i < 5; i++) { long startTime = System.nanoTime(); ExecutorService es = Executors.newFixedThreadPool(THREAD_POOL_SIZE); for (int j = 0; j < THREAD_POOL_SIZE; j++) { es.execute(new Runnable() { @Override public void run() { for (int i = 0; i < 500000; i++) { Integer randomNumber = (int) Math.ceil(Math.random() * 550000); map.put(String.valueOf(randomNumber), randomNumber); } } }); } es.shutdown(); es.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS); long entTime = System.nanoTime(); long totalTime = (entTime - startTime) / 1000000L; averageTime += totalTime; System.out.println("添加耗时" + totalTime + " ms"); } System.out.println("操作 " + map.getClass() + " 平均时间为 " + averageTime / 5 + " ms\n"); } }
