[DEV] add dffs formual impl interface

atms-api/src/main/java/pwc/taxtech/atms/vat/service/impl/ReportGeneratorImpl.java

@@ -574,7 +574,7 @@ public class ReportGeneratorImpl {
     public void addFunctionsAndContext(Workbook workbook, String[] functions, FormulaContext formulaContext) {
         FreeRefFunction[] functionImpls = {new SGSR(formulaContext), new FSJZ(formulaContext), new ND(formulaContext),
                 new BB(formulaContext), new XXFP(formulaContext), new GZSD(formulaContext), new ProjectContext(formulaContext)
-                , new JXFPMX(formulaContext), new JXFP(formulaContext),new PSUM(formulaContext)};
+                , new JXFPMX(formulaContext), new JXFP(formulaContext), new PSUM(formulaContext) ,new DFFS(formulaContext)};
         UDFFinder udfs = new DefaultUDFFinder(functions, functionImpls);
         UDFFinder udfToolpack = new AggregatingUDFFinder(udfs);
         workbook.addToolPack(udfToolpack);

atms-api/src/main/java/pwc/taxtech/atms/vat/service/impl/report/functions/DFFS.java

+package pwc.taxtech.atms.vat.service.impl.report.functions;
+
+import org.apache.poi.ss.formula.OperationEvaluationContext;
+import org.apache.poi.ss.formula.eval.NumberEval;
+import org.apache.poi.ss.formula.eval.ValueEval;
+import org.apache.poi.ss.formula.functions.FreeRefFunction;
+
+public class DFFS extends FunctionBase implements FreeRefFunction {
+    public DFFS(FormulaContext formulaContext) {
+        super(formulaContext);
+    }
+
+    @Override
+    public ValueEval evaluate(ValueEval[] args, OperationEvaluationContext ec) {
+        return new NumberEval(0);
+    }
+}