not higher order function added

Author: ozayduman

src/main/java/com/github/ozayduman/specificationbuilder/SpecificationOperator.java

@@ -122,16 +122,15 @@ static SpecificationOperator le(){
      */
     static SpecificationOperator in(){
         return (From<?,?> from, CriteriaBuilder cb,SingularAttribute attribute, Comparable[] values) ->
-                from.in(values);
+                from.get(attribute.getName()).in(values);
     }
 
     /**
      * Represents not in function
      * @return {@link SpecificationOperator}
      */
     static SpecificationOperator notIn(){
-        return (From<?,?> from, CriteriaBuilder cb,SingularAttribute attribute, Comparable[] values) ->
-                from.in(values).not();
+        return not(in());
     }
 
     /**
@@ -185,4 +184,14 @@ static SpecificationOperator like(){
     static SpecificationOperator notLike(){
         return (from, cb, attribute, values) -> cb.notLike(from.get(attribute.getName()), String.format("%%%s%%", values[0]));
     }
+
+    /** Represents a Higher Order Function that inverts a given {@code SpecificationOperator}
+     * @param operator is a Specification operator
+     * @return {@Link SpecificationOperator}
+     */
+    static SpecificationOperator not(SpecificationOperator operator){
+        return operator == null
+                ? (from, cb, attribute, values) -> null
+                : (from, cb, attribute, values) -> cb.not(operator.apply(from, cb, attribute, values));
+    }
 }