Java List First Item nullSafeAppend(List first, List second)

Description

This method joins two lists returning the a single list consisting of the first followed by the second.

License

Open Source License

Parameter

Parameter	Description
first	first list. can be null.
second	second list. can be null.

Return

the concatenation of both lists. will not be null

Declaration

public static <T> List<T> nullSafeAppend(List<T> first, List<T> second) 

Method Source Code

//package com.java2s;
/*/*from w w  w .  j a va 2s  .  co m*/
 * Copyright (C) 2005-2014 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco 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.
 *
 * Alfresco 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 Alfresco. If not, see <http://www.gnu.org/licenses/>.
 */

import java.util.ArrayList;

import java.util.Collection;

import java.util.List;
import java.util.Map;

public class Main {
    /**
     * This method joins two lists returning the a single list consisting of the first followed by the second.
     * 
     * @param first  first list. can be null.
     * @param second second list. can be null.
     * @return the concatenation of both lists. will not be null
     */
    public static <T> List<T> nullSafeAppend(List<T> first, List<T> second) {
        return nullSafeAppend(first, second, false);
    }

    /**
     * This method joins two lists returning the a single list consisting of the first followed by the second.
     * 
     * @param first  first list. can be null.
     * @param second second list. can be null.
     * @param emptyResultIsNull if the result is empty, should we return null?
     * @return the concatenation of both lists or null
     */
    public static <T> List<T> nullSafeAppend(List<T> first, List<T> second, boolean emptyResultIsNull) {
        List<T> result = new ArrayList<T>();

        if (first != null)
            result.addAll(first);
        if (second != null)
            result.addAll(second);

        if (result.isEmpty() && emptyResultIsNull) {
            result = null;
        }
        return result;
    }

    public static boolean isEmpty(Map<?, ?> map) {
        if (map == null) {
            return true;
        }
        return map.isEmpty();
    }

    public static boolean isEmpty(Collection<?> items) {
        if (items == null) {
            return true;
        }
        return items.isEmpty();
    }
}

Related

1. merge(List first, List second)
2. mergeLists(List first, List second)
3. mergeLists(List first, List second)
4. mergePreserveOrder(List first, List second)
5. moveItemKindInFirst(final List list)
6. orderByFirstOccurenceInText(String listToOrder[], String textToParse, boolean fuzzy)
7. orderByFuzzyFirstOccurenceInText(String listToOrder[], String textToParse)
8. permutationsWithFirstElement(List listings)
9. prepend(String first, List list)