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package com.tianmg.demo;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import java.util.HashMap;import java.util.Map;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Semaphore;public class MapExample { private static final Logger log = LoggerFactory.getLogger(MapExample.class); private static Map map = new HashMap(); private static int threadNum = 1; private static int clientNum = 5000; public static void main(String[] args) { ExecutorService exec = Executors.newCachedThreadPool(); final Semaphore semaphore = new Semaphore(threadNum); for (int index = 0; index < clientNum; index++) { final int threadNum = index; exec.execute(() -> { try { semaphore.acquire(); func(threadNum); semaphore.release(); } catch (Exception e) { log.error("exception", e); } }); } exec.shutdown(); log.info("size:{}", map.size()); } public static void func(int threadNum) { map.put(threadNum, threadNum); }}private static int threadNum = 1;代码中将上面这行代码的值改为1之后，程序运行的结果还是小于5000，这是什么原因？ |
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