com.eryansky.common.utils.collections.Collections3.java Source code

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Here is the source code for com.eryansky.common.utils.collections.Collections3.java

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/**
 *  Copyright (c) 2012-2014 http://www.eryansky.com
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 */
package com.eryansky.common.utils.collections;

import java.util.*;

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

import com.eryansky.common.utils.reflection.ReflectionUtils;

/**
 * Collections.
 * JDKCollectionsGuavaCollections2?, ??Collections3.
 * 
 * @author &Eryan eryanwcp@gmail.com
 */
public class Collections3 {

    /**
     * ????(Getter), ??Map.
     * 
     * @param collection ???.
     * @param keyPropertyName ????MapKey??.
     * @param valuePropertyName ????MapValue??.
     */
    @SuppressWarnings({ "rawtypes", "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 ReflectionUtils.convertReflectionExceptionToUnchecked(e);
        }

        return map;
    }

    /**
     * ????(Getter), ??List.
     * 
     * @param collection ???.
     * @param propertyName ??????.
     */
    @SuppressWarnings({ "rawtypes", "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 ReflectionUtils.convertReflectionExceptionToUnchecked(e);
        }

        return list;
    }

    /**
     * ????(Getter), ??.
     * 
     * @param collection ???.
     * @param propertyName ??????.
     * @param separator .
     */
    @SuppressWarnings("rawtypes")
    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(@SuppressWarnings("rawtypes") final Collection collection,
            final String separator) {
        return StringUtils.join(collection, separator);
    }

    /**
     * ?Collection(toString())String, ???prefix??postfix<div>mymessage</div>
     */
    public static String convertToString(@SuppressWarnings("rawtypes") 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();
    }

    /**
     * ?.
     */
    @SuppressWarnings("rawtypes")
    public static boolean isEmpty(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;
    }

    /**
     * ?list2list1??
     * ???List?hashcodeequals
     * A={2,3} comple B={1,1,2,6} => C={1,6}
     * @param a
     * @param b
     * @return
     * @throws Exception
     */
    @SuppressWarnings("unchecked")
    public static <T> List<T> comple(Collection<T> a, Collection<T> b) {
        Set<T> set = new LinkedHashSet();
        set.addAll(a);
        set.removeAll(intersection(a, b));
        return new ArrayList(set);
    }

    /**
     * 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;
    }

    /**
     * ab??List.
     */
    public static <T> List<T> aggregate(Collection<T> a, Collection<T> b) {
        List<T> list = new ArrayList<T>();
        if (a != null) {
            Iterator it = a.iterator();
            while (it.hasNext()) {
                T o = (T) it.next();
                if (!list.contains(o)) {
                    list.add(o);
                }
            }
        }
        if (b != null) {
            Iterator it = b.iterator();
            while (it.hasNext()) {
                T o = (T) it.next();
                if (!list.contains(o))
                    list.add(o);
            }
        }
        return list;
    }
}