update LruMemoryCache

Author: wyouflf

library/src/com/lidroid/xutils/cache/KeyExpiryMap.java

@@ -68,7 +68,8 @@ public synchronized Long put(K key, Long expiryTimestamp) {
     public synchronized boolean containsKey(Object key) {
         boolean result = false;
         if (super.containsKey(key)) {
-            if (System.currentTimeMillis() < super.get(key)) {
+            Long expiryTimestamp = super.get(key);
+            if (expiryTimestamp != null && System.currentTimeMillis() < expiryTimestamp) {
                 result = true;
             } else {
                 this.remove(key);

library/src/com/lidroid/xutils/cache/LruMemoryCache.java

@@ -69,14 +69,13 @@ public final V get(K key) {
             throw new NullPointerException("key == null");
         }
 
-        // If expired, remove the entry.
-        if (!keyExpiryMap.containsKey(key)) {
-            this.remove(key);
-            return null;
-        }
-
         V mapValue;
         synchronized (this) {
+            // If expired, remove the entry.
+            if (!keyExpiryMap.containsKey(key)) {
+                this.remove(key);
+                return null;
+            }
             mapValue = map.get(key);
             if (mapValue != null) {
                 hitCount++;