cayenne-server/src/main/java/org/apache/cayenne/exp/parser/ASTAvg.java

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 *  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
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package org.apache.cayenne.exp.parser;

import java.util.Collection;

import org.apache.cayenne.exp.Expression;

/**
 * @since 4.0
 */
public class ASTAvg extends ASTAggregateFunctionCall {

    ASTAvg(int id) {
        super(id, "AVG");
    }

    public ASTAvg(Expression expression) {
        super(ExpressionParserTreeConstants.JJTAVG, "AVG", expression);
    }

    @Override
    public Expression shallowCopy() {
        return new ASTAvg(id);
    }

    @Override
    protected Object evaluateCollection(Collection<?> values) {
        if(values.isEmpty()) {
            return 0.0;
        }

        double sum = 0;
        for(Object value : values) {
            if(value instanceof Number) {
                sum += ((Number) value).doubleValue();
            } else {
                throw new UnsupportedOperationException("Can't calculate average for non-numeric type.");
            }
        }

        return sum / values.size();
    }
}