aplcache

diff --git a/src/main/java/br/ufrgs/inf/prosoft/aplcache/caching/APLCache.java b/src/main/java/br/ufrgs/inf/prosoft/aplcache/caching/APLCache.java
index e966ebe..9a05f2a 100644
--- a/src/main/java/br/ufrgs/inf/prosoft/aplcache/caching/APLCache.java
+++ b/src/main/java/br/ufrgs/inf/prosoft/aplcache/caching/APLCache.java
@@ -17,6 +17,7 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Optional;
 import java.util.function.Supplier;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -34,7 +35,7 @@ public class APLCache<V> {
     private static String APLCACHE_CACHEABLE_PARAMETERS = System.getenv("APLCACHE_CACHEABLE_PARAMETERS");
     private static final Map<String, Collection<String>> APLCACHE_METHOD_HAS_CACHEABLE_PARAMETERS = new HashMap<>();
     private static final String APLCACHE_LOG = System.getenv("APLCACHE_LOG");
-    private final MultiCache<String, V> multiCache;
+    private final MultiCache<String, Optional<V>> multiCache;
 
     public APLCache() {
         this.multiCache = new MultiCache<>();
@@ -137,13 +138,14 @@ public class APLCache<V> {
 
         String serialisedParameters = Stream.of(parameters).map(JSONSerialiser::serialise)
                 .collect(Collectors.joining(",", "[", "]"));
-        V get = this.multiCache.get(serialisedParameters);
-        if (get != null) {
-            return get;
+        Optional<V> optional = this.multiCache.get(serialisedParameters);
+        if (optional != null) {
+            return optional.orElse(null);
         }
-        get = supplier.get();
+        V get = supplier.get();
+        optional = Optional.ofNullable(get);
         if (isCacheable(methodName, serialisedParameters)) {
-            this.multiCache.put(serialisedParameters, get, timeToLive);
+            this.multiCache.put(serialisedParameters, optional, timeToLive);
         }
         return get;
     }
@@ -160,13 +162,14 @@ public class APLCache<V> {
 
         String serialisedParameters = Stream.of(parameters).map(JSONSerialiser::serialise)
                 .collect(Collectors.joining(",", "[", "]"));
-        V get = this.multiCache.get(serialisedParameters);
-        if (get != null) {
-            return get;
+        Optional<V> optional = this.multiCache.get(serialisedParameters);
+        if (optional != null) {
+            return optional.orElse(null);
         }
-        get = supplier.get();
+        V get = supplier.get();
+        optional = Optional.ofNullable(get);
         if (isCacheable(methodName, serialisedParameters)) {
-            this.multiCache.put(serialisedParameters, get);
+            this.multiCache.put(serialisedParameters, optional);
         }
         return get;
     }