net.cloudkit.enterprises.infrastructure.utilities.Collections3Utility.java Source code

Introduction

Here is the source code for net.cloudkit.enterprises.infrastructure.utilities.Collections3Utility.java

Source

/*
 * Copyright (C) 2015 The Workbench Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.cloudkit.enterprises.infrastructure.utilities;

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

import java.util.*;

/**
 * Collections.
 * JDKCollectionsGuavaCollections2?, ??Collections3.
 * ????????Apache Commons Collection, ??
 *
 * @author hongquanli <hongquanli@qq.com>
 * @version 1.0 20131121 ?2:58:10
 */
public class Collections3Utility {

    /**
     * ????(Getter), ??Map.
     *
     * @param collection ???.
     * @param keyPropertyName ????MapKey??.
     * @param valuePropertyName ????MapValue??.
     */
    public static Map<Object, Object> extractToMap(final Collection<?> collection, final String keyPropertyName,
            final String valuePropertyName) {
        Map<Object, Object> map = new HashMap<Object, Object>(collection.size());

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

        return map;
    }

    /**
     * ????(Getter), ??List.
     *
     * @param collection ???.
     * @param propertyName ??????.
     */
    public static List<Object> extractToList(final Collection<?> collection, final String propertyName) {
        List<Object> list = new ArrayList<Object>(collection.size());

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

        return list;
    }

    /**
     * ????(Getter), ??.
     *
     * @param collection ???.
     * @param propertyName ??????.
     * @param separator .
     */
    public static String extractToString(final Collection<?> collection, final String propertyName,
            final String separator) {
        List<?> list = extractToList(collection, propertyName);
        return StringUtils.join(list, separator);
    }

    /**
     * ?Collection(toString())String,  separator
     */
    public static String convertToString(final Collection<?> collection, final String separator) {
        return StringUtils.join(collection, separator);
    }

    /**
     * ?Collection(toString())String, ???prefix??postfix<div>mymessage</div>
     */
    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();
    }

    /**
     * ?.
     */
    public static boolean isEmpty(Collection<?> collection) {
        return ((collection == null) || collection.isEmpty());
    }

    /**
     * ?.
     */
    public static boolean isNotEmpty(Collection<?> collection) {
        return ((collection != null) && !(collection.isEmpty()));
    }

    /**
     * ?Collectioncollectionnull.
     */
    public static <T> T getFirst(Collection<T> collection) {
        if (isEmpty(collection)) {
            return null;
        }

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

    /**
     * ?Collection? collectionnull.
     */
    public static <T> T getLast(Collection<T> collection) {
        if (isEmpty(collection)) {
            return null;
        }

        // List?? 
        if (collection instanceof List) {
            List<T> list = (List<T>) collection;
            return list.get(list.size() - 1);
        }

        // iterator?.
        Iterator<T> iterator = collection.iterator();
        while (true) {
            T current = iterator.next();
            if (!iterator.hasNext()) {
                return current;
            }
        }
    }

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

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

        return list;
    }

    /**
     * abList.
     */
    public static <T> List<T> intersection(Collection<T> a, Collection<T> b) {
        List<T> list = new ArrayList<T>();

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