--- /dev/null
+package org.apache.poi.hssf.record.formula.functions;
+
+import java.util.Calendar;
+import java.util.GregorianCalendar;
+
+import org.apache.poi.hssf.record.formula.eval.EvaluationException;
+import org.apache.poi.ss.usermodel.DateUtil;
+
+/**
+ * Calculates the number of days between two dates based on a 360-day year
+ * (twelve 30-day months), which is used in some accounting calculations. Use
+ * this function to help compute payments if your accounting system is based on
+ * twelve 30-day months.
+ *
+ *
+ * @author PUdalau
+ */
+public class Days360 extends NumericFunction.TwoArg {
+
+ @Override
+ protected double evaluate(double d0, double d1) throws EvaluationException {
+ Calendar startingDate = getStartingDate(d0);
+ Calendar endingDate = getEndingDateAccordingToStartingDate(d1, startingDate);
+ long startingDay = startingDate.get(Calendar.MONTH) * 30 + startingDate.get(Calendar.DAY_OF_MONTH);
+ long endingDay = (endingDate.get(Calendar.YEAR) - startingDate.get(Calendar.YEAR)) * 360
+ + endingDate.get(Calendar.MONTH) * 30 + endingDate.get(Calendar.DAY_OF_MONTH);
+ return endingDay - startingDay;
+ }
+
+ private Calendar getDate(double date) {
+ Calendar processedDate = new GregorianCalendar();
+ processedDate.setTime(DateUtil.getJavaDate(date, false));
+ return processedDate;
+ }
+
+ private Calendar getStartingDate(double date) {
+ Calendar startingDate = getDate(date);
+ if (isLastDayOfMonth(startingDate)) {
+ startingDate.set(Calendar.DAY_OF_MONTH, 30);
+ }
+ return startingDate;
+ }
+
+ private Calendar getEndingDateAccordingToStartingDate(double date, Calendar startingDate) {
+ Calendar endingDate = getDate(date);
+ endingDate.setTime(DateUtil.getJavaDate(date, false));
+ if (isLastDayOfMonth(endingDate)) {
+ if (startingDate.get(Calendar.DATE) < 30) {
+ endingDate = getFirstDayOfNextMonth(endingDate);
+ }
+ }
+ return endingDate;
+ }
+
+ private boolean isLastDayOfMonth(Calendar date) {
+ Calendar clone = (Calendar) date.clone();
+ clone.add(java.util.Calendar.MONTH, 1);
+ clone.add(java.util.Calendar.DAY_OF_MONTH, -1);
+ int lastDayOfMonth = clone.get(Calendar.DAY_OF_MONTH);
+ return date.get(Calendar.DAY_OF_MONTH) == lastDayOfMonth;
+ }
+
+ private Calendar getFirstDayOfNextMonth(Calendar date) {
+ Calendar newDate = (Calendar) date.clone();
+ if (date.get(Calendar.MONTH) < Calendar.DECEMBER) {
+ newDate.set(Calendar.MONTH, date.get(Calendar.MONTH) + 1);
+ } else {
+ newDate.set(Calendar.MONTH, 1);
+ newDate.set(Calendar.YEAR, date.get(Calendar.YEAR) + 1);
+ }
+ newDate.set(Calendar.DATE, 1);
+ return newDate;
+ }
+}
--- /dev/null
+/* ====================================================================
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+==================================================================== */
+
+package org.apache.poi.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.EvaluationException;
+
+/**
+ * Calculates the net present value of an investment by using a discount rate
+ * and a series of future payments (negative values) and income (positive
+ * values). Minimum 2 arguments, first arg is the rate of discount over the
+ * length of one period others up to 254 arguments representing the payments and
+ * income.
+ *
+ * @author SPetrakovsky
+ */
+public class Npv extends NumericFunction.MultiArg {
+
+ public Npv() {
+ super(2, 255);
+ }
+
+ @Override
+ protected double evaluate(double[] ds) throws EvaluationException {
+ double rate = ds[0];
+ double sum = 0;
+ for (int i = 1; i < ds.length; i++) {
+ sum += ds[i] / Math.pow(rate + 1, i);
+ }
+ return sum;
+ }
+
+}