Java List Max findMaximalMatch(List> mapList, LinkedHashMap fieldsByPriority)

Description

For a list of Map find the entry that best matches the fieldsByPriority Ordered Map; null field values in a Map in mapList match against any value but do not contribute to maximal match score, otherwise value for each field in fieldsByPriority must match for it to be a candidate.

License

Creative Commons License

Declaration

public static Map<String, Object> findMaximalMatch(List<Map<String, Object>> mapList,
        LinkedHashMap<String, Object> fieldsByPriority) 

Method Source Code

//package com.java2s;
/*// ww  w.  ja v  a2  s  .c om
 * 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.util.*;

public class Main {
    /**
     * For a list of Map find the entry that best matches the fieldsByPriority Ordered Map; null field values in a Map
     * in mapList match against any value but do not contribute to maximal match score, otherwise value for each field
     * in fieldsByPriority must match for it to be a candidate.
     */
    public static Map<String, Object> findMaximalMatch(List<Map<String, Object>> mapList,
            LinkedHashMap<String, Object> fieldsByPriority) {
        int numFields = fieldsByPriority.size();
        String[] fieldNames = new String[numFields];
        Object[] fieldValues = new Object[numFields];
        int index = 0;
        for (Map.Entry<String, Object> entry : fieldsByPriority.entrySet()) {
            fieldNames[index] = entry.getKey();
            fieldValues[index] = entry.getValue();
            index++;
        }

        int highScore = -1;
        Map<String, Object> highMap = null;
        for (Map<String, Object> curMap : mapList) {
            int curScore = 0;
            boolean skipMap = false;
            for (int i = 0; i < numFields; i++) {
                String curField = fieldNames[i];
                Object compareValue = fieldValues[i];
                // if curMap value is null skip field (null value in Map means allow any match value
                Object curValue = curMap.get(curField);
                if (curValue == null)
                    continue;
                // if not equal skip Map
                if (!curValue.equals(compareValue)) {
                    skipMap = true;
                    break;
                }
                // add to score based on index (lower index higher score), also add numFields so more fields matched weights higher
                curScore += (numFields - i) + numFields;
            }

            if (skipMap)
                continue;
            // have a higher score?
            if (curScore > highScore) {
                highScore = curScore;
                highMap = curMap;
            }
        }

        return highMap;
    }
}

Related

1. findMax(List nums)
2. findMax(List values)
3. findMaxDeformationCount(final List counts)
4. getMax(List numList)
5. getMax(List aList)
6. getMax(List d)
7. getMax(List list)