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/**
 * 本作品使用 木兰公共许可证,第2版（Mulan PubL v2） 开源协议，请遵守相关条款，或者联系sicheng.net获取商用授权。
 * Copyright (c) 2016 SiCheng.Net
 * This software is licensed under Mulan PubL v2.
 * You can use this software according to the terms and conditions of the Mulan PubL v2.
 * You may obtain a copy of Mulan PubL v2 at:
 *          http://license.coscl.org.cn/MulanPubL-2.0
 * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
 * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
 * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
 * See the Mulan PubL v2 for more details.
 */
package com.sicheng.common.utils;

import org.apache.commons.beanutils.PropertyUtils;
import org.apache.commons.lang3.StringUtils;

import java.util.*;

/**
 * Collections工具集.
 * 在JDK的Collections和Guava的Collections2后, 命名为Collections3.
 *
 * @author zhaolei
 * @version 2013-01-15
 */
@SuppressWarnings("rawtypes")
public class Collections3 {

    /**
     * 提取集合中的对象的两个属性(通过Getter函数), 组合成Map.
     *
     * @param collection        来源集合.
     * @param keyPropertyName   要提取为Map中的Key值的属性名.
     * @param valuePropertyName 要提取为Map中的Value值的属性名.
     */
    @SuppressWarnings("unchecked")
    public static Map extractToMap(final Collection collection, final String keyPropertyName,
                                   final String valuePropertyName) {
        Map map = new HashMap(collection.size());

        try {
            for (Object obj : collection) {
                map.put(PropertyUtils.getProperty(obj, keyPropertyName),
                        PropertyUtils.getProperty(obj, valuePropertyName));
            }
        } catch (Exception e) {
            throw Reflections.convertReflectionExceptionToUnchecked(e);
        }

        return map;
    }

    /**
     * 提取集合中的对象的一个属性(通过Getter函数), 组合成List.
     *
     * @param collection   来源集合.
     * @param propertyName 要提取的属性名.
     */
    @SuppressWarnings("unchecked")
    public static List extractToList(final Collection collection, final String propertyName) {
        List list = new ArrayList(collection.size());

        try {
            for (Object obj : collection) {
                list.add(PropertyUtils.getProperty(obj, propertyName));
            }
        } catch (Exception e) {
            throw Reflections.convertReflectionExceptionToUnchecked(e);
        }

        return list;
    }

    /**
     * 提取集合中的对象的一个属性(通过Getter函数), 组合成由分割符分隔的字符串.
     *
     * @param collection   来源集合.
     * @param propertyName 要提取的属性名.
     * @param separator    分隔符.
     */
    public static String extractToString(final Collection collection, final String propertyName, final String separator) {
        List list = extractToList(collection, propertyName);
        return StringUtils.join(list, separator);
    }

    /**
     * 转换Collection所有元素(通过toString())为String, 中间以 separator分隔。
     */
    public static String convertToString(final Collection collection, final String separator) {
        return StringUtils.join(collection, separator);
    }

    /**
     * 转换Collection所有元素(通过toString())为String, 每个元素的前面加入prefix，后面加入postfix，如mymessage。
     */
    public static String convertToString(final Collection collection, final String prefix, final String postfix) {
        StringBuilder builder = new StringBuilder();
        for (Object o : collection) {
            builder.append(prefix).append(o).append(postfix);
        }
        return builder.toString();
    }

    /**
     * 判断是否为空.
     */
    public static boolean isEmpty(Collection collection) {
        return (collection == null || collection.isEmpty());
    }

    /**
     * 取得Collection的第一个元素，如果collection为空返回null.
     */
    public static  T getFirst(Collection collection) {
        if (isEmpty(collection)) {
            return null;
        }

        return collection.iterator().next();
    }

    /**
     * 获取Collection的最后一个元素 ，如果collection为空返回null.
     */
    public static  T getLast(Collection collection) {
        if (isEmpty(collection)) {
            return null;
        }

        //当类型为List时，直接取得最后一个元素 。
        if (collection instanceof List) {
            List list = (List) collection;
            return list.get(list.size() - 1);
        }

        //其他类型通过iterator滚动到最后一个元素.
        Iterator iterator = collection.iterator();
        while (true) {
            T current = iterator.next();
            if (!iterator.hasNext()) {
                return current;
            }
        }
    }

    /**
     * 返回a+b的新List.
     */
    public static  List union(final Collection a, final Collection b) {
        List result = new ArrayList(a);
        result.addAll(b);
        return result;
    }

    /**
     * 返回a-b的新List.
     */
    public static  List subtract(final Collection a, final Collection b) {
        List list = new ArrayList(a);
        for (T element : b) {
            list.remove(element);
        }

        return list;
    }

    /**
     * 返回a与b的交集的新List.
     */
    public static  List intersection(Collection a, Collection b) {
        List list = new ArrayList();

        for (T element : a) {
            if (b.contains(element)) {
                list.add(element);
            }
        }
        return list;
    }
}