com.personal.tools.Collections3.java Source code

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Here is the source code for com.personal.tools.Collections3.java

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/**
 * Copyright (c) 2005-2012 springside.org.cn
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License");
 */
package com.personal.tools;

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

import java.util.*;

/**
 * Collections.
 * <p>
 * JDKCollectionsGuavaCollections2?, ??Collections3.
 * <p>
 * ????????Apache Commons Collection, ??
 *
 * @author calvin
 */
public class Collections3 {

    /**
     * ????(Getter), ??Map.
     *
     * @param collection        ???.
     * @param keyPropertyName   ????MapKey??.
     * @param valuePropertyName ????MapValue??.
     */
    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;
    }

    /**
     * ????(Getter), ??List.
     *
     * @param collection   ???.
     * @param propertyName ??????.
     */
    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;
    }

    /**
     * ????(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<>(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<>(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<>();

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