Simplify the implementation of memoizeSupplier.

cyclops/src/main/java/cyclops/function/Memoize.java

@@ -23,28 +23,25 @@
 import lombok.val;
 
 public class Memoize {
-    private final static Object UNSET = new Object();
+
     /**
      * Convert a Supplier into one that caches it's result
      *
      * @param s Supplier to memoise
      * @return Memoised Supplier
      */
     public static <T> Function0<T> memoizeSupplier(final Supplier<T> s) {
-        AtomicReference value = new AtomicReference<>(
-            UNSET);
-        return ()->{
-            Object val = value.get();
-        if (val == UNSET) {
-            synchronized (value){
-                if(value.get()==UNSET) {
-                    val = s.get();
-                    value.set(val);
+        final AtomicReference<T> atomic = new AtomicReference<>(null);
+        return () -> {
+            if (atomic.get() == null) {
+                synchronized (atomic) {
+                    if (atomic.get() == null) {
+                        T val = s.get();
+                        atomic.set(val);
+                    }
                 }
             }
-        }
-
-        return (T)val;
+            return atomic.get();
         };
 
     }