better toString support for improved log messages

Change-Id: I00fd950667bb7597ab7972cc76480234b15d00d1

java/com.sap.sse/src/com/sap/sse/util/SmartFutureCache.java

@@ -194,6 +194,10 @@ public class SmartFutureCache<K, V, U extends UpdateInterval<U>> {
             return callable.call();
         }
         
+        @Override
+        public String toString() {
+            return callable==null?"null":callable.toString();
+        }
     }
     
     /**
@@ -377,6 +381,11 @@ public class SmartFutureCache<K, V, U extends UpdateInterval<U>> {
         public void setExecutorThisTaskIsScheduledFor(ThreadPoolExecutor executorThisTaskIsScheduledFor) {
             tracingGetHelper.setExecutorThisTaskIsScheduledFor(executorThisTaskIsScheduledFor);
         }
+        
+        @Override
+        public String toString() {
+            return getClass().getName()+" [key="+key+", updateInterval="+updateInterval+", cacheUpdateComputer="+cacheUpdateComputer+"]";
+        }
     }
     
     public SmartFutureCache(CacheUpdater<K, V, U> cacheUpdateComputer, String nameForLocks) {