1、实现代码
import java.util.HashMap; import java.util.concurrent.ConcurrentHashMap; public class LocalCache { private LocalCache() { } // 防止在外部实例化 // 使用volatile延迟初始化，防止编译器重排序 private static volatile LocalCache instance; public static LocalCache getInstance() { // 对象实例化时与否判断（不使用同步代码块，instance不等于null时，直接返回对象，提高运行效率） if (instance == null) { // 同步代码块（对象未初始化时，使用同步代码块，保证多线程访问时对象在第一次创建后，不再重复被创建） synchronized (LocalCache.class) { // 未初始化，则初始instance变量 if (instance == null) { instance = new LocalCache(); } } } return instance; } protected static final ConcurrentHashMap<String, Object> dataMap = new ConcurrentHashMap<String, Object>(); private static final Object lock = new Object(); public static Object get(String key) { Object v = dataMap.get(key); if (v == null) { synchronized (lock) { v = dataMap.get(key); // Check again to avoid re-load } } return v; } public static synchronized void set(String key, Object value) { dataMap.put(key, value); } public static synchronized boolean isAccess(String ip, long maxTimeInterval, long maxTimes) { @SuppressWarnings("unchecked") HashMap<String, Object> map = (HashMap<String, Object>) dataMap.get(ip); if (null == map) { map = new HashMap<String, Object>(); map.put("times", 1); map.put("timestamp", System.currentTimeMillis()); LocalCache.set(ip, map); System.err.println(ip+":"+map); return true; } else { int times = (int) map.get("times"); long timestamp = (long) map.get("timestamp"); if (System.currentTimeMillis() - timestamp > maxTimeInterval*1000) { map.put("times", 1); map.put("timestamp", System.currentTimeMillis()); LocalCache.set(ip, map); System.err.println(ip+":"+map); return true; } else { if (times < maxTimes) { map.put("times", times + 1); LocalCache.set(ip, map); System.err.println(ip+":"+map); return true; } else { System.err.println("false"); return false; } } } } } 2、测试代码 import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import com.seed.file.util.cache.LocalCache; public class LocalCacheTest implements Runnable { @Override public void run() { LocalCache.isAccess("127.0.0.1", 3000L, 3); } public static void main(String[] args) { ExecutorService pool = Executors.newCachedThreadPool(); LocalCacheTest test = new LocalCacheTest(); for (int i = 0; i < 100; i++) { pool.execute(test); } } } 3、测试结果127.0.0.1:{times=1, timestamp=1496801373728} 127.0.0.1:{times=2, timestamp=1496801373728} 127.0.0.1:{times=3, timestamp=1496801373728} false false false false false false false
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