Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
/*
 * This software is in the public domain under CC0 1.0 Universal plus a
 * Grant of Patent License.
 *
 * To the extent possible under law, the author(s) have dedicated all
 * copyright and related and neighboring rights to this software to the
 * public domain worldwide. This software is distributed without any
 * warranty.
 *
 * You should have received a copy of the CC0 Public Domain Dedication
 * along with this software (see the LICENSE.md file). If not, see
 * <http://creativecommons.org/publicdomain/zero/1.0/>.
 */

import java.math.BigDecimal;

import java.util.*;

public class Main {
    /** Returns Map with total, squaredTotal, count, average, stdDev, maximum; fieldName field in Maps must have type BigDecimal;
     * if count of non-null fields is less than 2 returns null as cannot calculate a standard deviation */
    public static Map<String, BigDecimal> stdDevMaxFromMapField(List<Map<String, Object>> dataList,
            String fieldName, BigDecimal stdDevMultiplier) {
        BigDecimal total = BigDecimal.ZERO;
        BigDecimal squaredTotal = BigDecimal.ZERO;
        int count = 0;
        for (Map<String, Object> dataMap : dataList) {
            if (dataMap == null)
                continue;
            BigDecimal value = (BigDecimal) dataMap.get(fieldName);
            if (value == null)
                continue;
            total = total.add(value);
            squaredTotal = squaredTotal.add(value.multiply(value));
            count++;
        }
        if (count < 2)
            return null;

        BigDecimal countBd = new BigDecimal(count);
        BigDecimal average = total.divide(countBd, BigDecimal.ROUND_HALF_UP);
        double totalDouble = total.doubleValue();
        BigDecimal stdDev = new BigDecimal(Math
                .sqrt(Math.abs(squaredTotal.doubleValue() - ((totalDouble * totalDouble) / count)) / (count - 1)));

        Map<String, BigDecimal> retMap = new HashMap<>(6);
        retMap.put("total", total);
        retMap.put("squaredTotal", squaredTotal);
        retMap.put("count", countBd);
        retMap.put("average", average);
        retMap.put("stdDev", stdDev);

        if (stdDevMultiplier != null)
            retMap.put("maximum", average.add(stdDev.multiply(stdDevMultiplier)));

        return retMap;
    }
}