package mthashmap; import java.util.HashMap; import java.util.concurrent.ConcurrentHashMap; /** * @Ay叔 一个static 的MAP 里面 存了一个 实例..两条线程访问这个MAP 取这实例. 那么取到的是同一个 还是 两个不同的实例? * Created by zhida on 2015/2/12. */ public class MT_HashMap { public static ConcurrentHashMap<String, value> map = new ConcurrentHashMap<String, value>(); public static void main (String[] args){ map.put("key",new value("value")); new Thread(new Runnable(){ @Override public synchronized void run() { value v = map.get("key"); System.out.println("mt1 oldkey=" + v); try { Thread.currentThread().sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("mt1 mapkey = "+map.get("key")); System.out.println("mt1 key="+v); // map.put("key",new value("old value")); v.set("old value"); } }).start(); new Thread(new Runnable(){ @Override public synchronized void run() { try { Thread.currentThread().sleep(200); value v = map.get("key"); System.out.println("mt2 key="+v); v.set("new value"); // map.put("key",new value("new value")); System.out.println("mt2 mapkey="+map.get("key")); Thread.currentThread().sleep(1500); System.out.println("mt2 key="+v); } catch (InterruptedException e) { e.printStackTrace(); } } }).start(); } static class value{ String str; public value(String str){ this.str = str; } public void set(String str){ this.str = str; } public String toString(){ return str; } } }