poi/examples/src/main/java/org/apache/poi/examples/ss/formula/UserDefinedFunctionExample.java

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   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
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       http://www.apache.org/licenses/LICENSE-2.0

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   distributed under the License is distributed on an "AS IS" BASIS,
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   See the License for the specific language governing permissions and
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package org.apache.poi.examples.ss.formula;

import java.io.File;

import org.apache.poi.ss.formula.functions.FreeRefFunction;
import org.apache.poi.ss.formula.udf.DefaultUDFFinder;
import org.apache.poi.ss.formula.udf.UDFFinder;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellValue;
import org.apache.poi.ss.usermodel.FormulaEvaluator;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.usermodel.WorkbookFactory;
import org.apache.poi.ss.util.CellReference;


/**
 * An example class of how to invoke a User Defined Function for a given
 * XLS instance using POI's UDFFinder implementation.
 */
@SuppressWarnings({"java:S106","java:S4823","java:S1192"})
public final class UserDefinedFunctionExample {

    private UserDefinedFunctionExample() {}

    public static void main(String[] args ) throws Exception {

        if(  args.length != 2 ) {
            // e.g. src/examples/src/org/apache/poi/ss/examples/formula/mortgage-calculation.xls Sheet1!B4
            System.out.println( "usage: UserDefinedFunctionExample fileName cellId" ) ;
            return;
        }

        System.out.println( "fileName: " + args[0] ) ;
        System.out.println( "cell: " + args[1] ) ;

        File workbookFile = new File( args[0] ) ;

        try (Workbook workbook = WorkbookFactory.create(workbookFile, null, true)) {
            String[] functionNames = {"calculatePayment"};
            FreeRefFunction[] functionImpls = {new CalculateMortgage()};

            UDFFinder udfToolpack = new DefaultUDFFinder(functionNames, functionImpls);

            // register the user-defined function in the workbook
            workbook.addToolPack(udfToolpack);

            FormulaEvaluator evaluator = workbook.getCreationHelper().createFormulaEvaluator();

            CellReference cr = new CellReference(args[1]);
            String sheetName = cr.getSheetName();
            Sheet sheet = workbook.getSheet(sheetName);
            int rowIdx = cr.getRow();
            int colIdx = cr.getCol();
            Row row = sheet.getRow(rowIdx);
            Cell cell = row.getCell(colIdx);

            CellValue value = evaluator.evaluate(cell);

            System.out.println("returns value: " + value);
        }
    }
}