問題描述

1.設(shè)計了一個接口用于包裝其它 pojo，以計算是否過期

public interface CatchWrapper<T>{ public long getCatchedTime();public T getValue();public boolean valid();}

某一個實現(xiàn)：

public class DeviceCatchWrapper implements CatchWrapper<Device> { private final long catchedTime; private final Device device; private static final long CATCH_TIME = 20*1000; public DeviceCatchWrapper(Device device) {this.device = device;catchedTime = System.currentTimeMillis(); } @Override public long getCatchedTime() {return catchedTime; } @Override public Device getValue() {return device; } @Override public boolean valid() {return System.currentTimeMillis() - catchedTime < CATCH_TIME; }}

另有一個管理類，主要是刪除過期的緩存

public class DeviceCatchWrapperManager<T> { private static final ScheduledExecutorService service = Executors.newSingleThreadScheduledExecutor(); private final ConcurrentMap<String, CatchWrapper<T>> catchStore; private final long initialDelay; private final long delay; private TimeUnit unit; private volatile boolean stop = false; public DeviceCatchWrapperManager(ConcurrentMap<String,CatchWrapper<T>> catchStore, long initialDelay, long delay, TimeUnit unit) {this.catchStore = catchStore;this.initialDelay = initialDelay;this.delay = delay;this.unit = unit; } /** * 周期性檢查過期的緩存，然后刪除 */ public void startLoop() {service.scheduleWithFixedDelay(new Runnable() { @Override public void run() {for (Entry<String, CatchWrapper<T>> entry : catchStore.entrySet()) { if (stop)break; String key = entry.getKey(); CatchWrapper<T> cw = entry.getValue(); if (!cw.valid()){System.out.println('Device catch manager --------------->remove:'+key);catchStore.remove(key, cw); }} }}, initialDelay, delay, unit); } /** * 停在對緩存進(jìn)行過期檢查 */ public void stop() {stop = true;service.shutdownNow(); }}

但是真正構(gòu)造函數(shù) 傳參數(shù)報錯

private final ConcurrentMap<String, DeviceCatchWrapper> catchMap = new ConcurrentHashMap<>(); 下面的報錯，參數(shù)不對private final DeviceCatchWrapperManager<Device> catchManager = new DeviceCatchWrapperManager<Device>(catchMap, 2, 2, TimeUnit.HOURS);

改怎么解決這個錯誤 或者 該怎么設(shè)計接口或者改進(jìn)呢？

問題解答

ConcurrentMap<String, DeviceCatchWrapper> catchMap = new ConcurrentHashMap<>(); 這句有問題改成ConcurrentMap<String, CatchWrapper<Device>> catchMap = new ConcurrentHashMap<String, DeviceCatchWrapper>();試試