main/src/main/java/org/apache/poi/ss/formula/functions/DMax.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
   the License.  You may obtain a copy of the License at

       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.ss.formula.functions;

import org.apache.poi.ss.formula.eval.NumberEval;
import org.apache.poi.ss.formula.eval.NumericValueEval;
import org.apache.poi.ss.formula.eval.ValueEval;

/**
 * Implementation of the DMax function:
 * Finds the maximum value of a column in an area with given conditions.
 * 
 * TODO:
 * - wildcards ? and * in string conditions
 * - functions as conditions
 */
public final class DMax implements IDStarAlgorithm {
    private ValueEval maximumValue;

    @Override
    public boolean processMatch(ValueEval eval) {
        if(eval instanceof NumericValueEval) {
            if(maximumValue == null) { // First match, just set the value.
                maximumValue = eval;
            } else { // There was a previous match, find the new minimum.
                double currentValue = ((NumericValueEval)eval).getNumberValue();
                double oldValue = ((NumericValueEval)maximumValue).getNumberValue();
                if(currentValue > oldValue) {
                    maximumValue = eval;
                }
            }
        }

        return true;
    }

    @Override
    public ValueEval getResult() {
        if(maximumValue == null) {
            return NumberEval.ZERO;
        } else {
            return maximumValue;
        }
    }
}