Java List Combine combineAux(List<Collection<E>> collections, List<E> objectAccumulator, List<Collection<E>> resultList)

Description

Recursive auxiliary for combine(collections).

License

Open Source License

Declaration

private static <E> void combineAux(List<Collection<E>> collections, List<E> objectAccumulator,
        List<Collection<E>> resultList)

Method Source Code


//package com.java2s;
/*/*from   ww  w  . jav a 2 s.co  m*/
Copyright 2009 Semantic Discovery, Inc. (www.semanticdiscovery.com)
    
This file is part of the Semantic Discovery Toolkit.
    
The Semantic Discovery Toolkit is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
    
The Semantic Discovery Toolkit is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.
    
You should have received a copy of the GNU Lesser General Public License
along with The Semantic Discovery Toolkit.  If not, see <http://www.gnu.org/licenses/>.
*/

import java.util.List;
import java.util.ArrayList;

import java.util.Collection;
import java.util.Iterator;

public class Main {
    /** Recursive auxiliary for combine(collections). */
    private static <E> void combineAux(List<Collection<E>> collections, List<E> objectAccumulator,
            List<Collection<E>> resultList) {

        int numCollections = collections.size();

        if (numCollections == 0) {
            return;
        }

        Collection<E> firstCollection = collections.iterator().next();
        boolean isEmpty = firstCollection == null || firstCollection.size() == 0;

        if (numCollections == 1) {
            if (!isEmpty) {
                for (Iterator<E> it = firstCollection.iterator(); it.hasNext();) {
                    E curObject = it.next();
                    List<E> nextAccumulator = new ArrayList<E>(objectAccumulator);

                    nextAccumulator.add(curObject);
                    resultList.add(nextAccumulator);
                }
            } else {
                List<E> nextAccumulator = new ArrayList<E>(objectAccumulator);
                nextAccumulator.add(null);
                resultList.add(nextAccumulator);
            }
            return;
        }

        List<Collection<E>> remainder = collections.subList(1, numCollections);

        if (!isEmpty) {
            for (Iterator<E> it = firstCollection.iterator(); it.hasNext();) {
                E curObject = it.next();
                List<E> nextAccumulator = new ArrayList<E>(objectAccumulator);
                nextAccumulator.add(curObject);
                combineAux(remainder, nextAccumulator, resultList);
            }
        } else {
            List<E> nextAccumulator = new ArrayList<E>(objectAccumulator);
            nextAccumulator.add(null);
            combineAux(remainder, nextAccumulator, resultList);
        }
    }
}

Java List Combine combineAux(List> collections, List objectAccumulator, List> resultList)

Description

License

Declaration

Method Source Code

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