解决方案三（并发容器：ConcurrentHashMap）（对应 HashMap）
package com.mmall.concurrency.example.concurrent; import com.mmall.concurrency.annoations.ThreadSafe; import lombok.extern.slf4j.Slf4j; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Semaphore; @Slf4j @ThreadSafe public class ConcurrentHashMapExample { // 请求总数 public static int clientTotal = 5000; // 同时并发执行的线程数 public static int threadTotal = 200; private static Map<Integer, Integer> map = new ConcurrentHashMap<>(); public static void main(String[] args) throws Exception { ExecutorService executorService = Executors.newCachedThreadPool(); final Semaphore semaphore = new Semaphore(threadTotal); final CountDownLatch countDownLatch = new CountDownLatch(clientTotal); for (int i = 0; i < clientTotal; i++) { final int count = i; executorService.execute(() -> { try { semaphore.acquire(); update(count); semaphore.release(); } catch (Exception e) { log.error("exception", e); } countDownLatch.countDown(); }); } countDownLatch.await(); executorService.shutdown(); log.info("size:{}", map.size()); } private static void update(int i) { map.put(i, i); } } // 输出 size:5000
解决方案四（并发容器：ConcurrentSkipListMap）（对应 TreeMap）
package com.mmall.concurrency.example.concurrent; import com.mmall.concurrency.annoations.ThreadSafe; import lombok.extern.slf4j.Slf4j; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentSkipListMap; import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Semaphore; @Slf4j @ThreadSafe public class ConcurrentSkipListMapExample { // 请求总数 public static int clientTotal = 5000; // 同时并发执行的线程数 public static int threadTotal = 200; private static Map<Integer, Integer> map = new ConcurrentSkipListMap<>(); public static void main(String[] args) throws Exception { ExecutorService executorService = Executors.newCachedThreadPool(); final Semaphore semaphore = new Semaphore(threadTotal); final CountDownLatch countDownLatch = new CountDownLatch(clientTotal); for (int i = 0; i < clientTotal; i++) { final int count = i; executorService.execute(() -> { try { semaphore.acquire(); update(count); semaphore.release(); } catch (Exception e) { log.error("exception", e); } countDownLatch.countDown(); }); } countDownLatch.await(); executorService.shutdown(); log.info("size:{}", map.size()); } private static void update(int i) { map.put(i, i); } } // 输出 size:5000
ConcurrentSkipListMap和ConcurrentHashMap的区别
- ConcurrentHashMap 在不高并发下性能更好
- ConcurrentSkipListMap 在高并发下性能更好，且key是有序的
