001/*
002  GRANITE DATA SERVICES
003  Copyright (C) 2011 GRANITE DATA SERVICES S.A.S.
004
005  This file is part of Granite Data Services.
006
007  Granite Data Services is free software; you can redistribute it and/or modify
008  it under the terms of the GNU Library General Public License as published by
009  the Free Software Foundation; either version 2 of the License, or (at your
010  option) any later version.
011
012  Granite Data Services is distributed in the hope that it will be useful, but
013  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
014  FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License
015  for more details.
016
017  You should have received a copy of the GNU Library General Public License
018  along with this library; if not, see <http://www.gnu.org/licenses/>.
019*/
020
021package org.granite.util;
022
023import java.lang.reflect.ParameterizedType;
024import java.lang.reflect.Type;
025import java.util.ArrayList;
026import java.util.Collection;
027import java.util.HashSet;
028import java.util.Set;
029import java.util.SortedSet;
030import java.util.TreeSet;
031
032/**
033 * @author Franck WOLFF
034 */
035public class CollectionUtil {
036
037    public static Type getComponentType(Type collectionType) {
038
039        Class<?> collectionClass = TypeUtil.classOfType(collectionType);
040        if (collectionClass == null || !Collection.class.isAssignableFrom(collectionClass))
041            return null;
042
043        if (collectionType instanceof ParameterizedType) {
044            Type[] componentTypes = ((ParameterizedType)collectionType).getActualTypeArguments();
045            if (componentTypes != null && componentTypes.length == 1)
046                return componentTypes[0];
047        }
048
049        return Object.class;
050    }
051
052    @SuppressWarnings("unchecked")
053    public static Collection<Object> newCollection(Class<?> targetClass, int length)
054        throws InstantiationException, IllegalAccessException  {
055
056        if (targetClass.isInterface()) {
057
058            if (Set.class.isAssignableFrom(targetClass)) {
059                if (SortedSet.class.isAssignableFrom(targetClass))
060                    return new TreeSet<Object>();
061                return new HashSet<Object>(length);
062            }
063
064            if (targetClass.isAssignableFrom(ArrayList.class))
065                return new ArrayList<Object>(length);
066
067            throw new IllegalArgumentException("Unsupported collection interface: " + targetClass);
068        }
069
070        return (Collection<Object>)targetClass.newInstance();
071    }
072}