com.github.drinkjava2.cglib.core.CollectionUtils Maven / Gradle / Ivy

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/*
 * Copyright 2003,2004 The Apache Software Foundation
 *
 *  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 com.github.drinkjava2.cglib.core;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

/**
 * @author Chris Nokleberg
 * @version $Id: CollectionUtils.java,v 1.7 2004/06/24 21:15:21 herbyderby Exp $
 */
@SuppressWarnings({"rawtypes","unchecked"})    
public class CollectionUtils {
    private CollectionUtils() { }

    public static Map bucket(Collection c, Transformer t) {
        Map buckets = new HashMap();
        for (Iterator it = c.iterator(); it.hasNext();) {
            Object value = (Object)it.next();
            Object key = t.transform(value);
            List bucket = (List)buckets.get(key);
            if (bucket == null) {
                buckets.put(key, bucket = new LinkedList());
            }
            bucket.add(value);
        }
        return buckets;
    }

    public static void reverse(Map source, Map target) {
        for (Iterator it = source.keySet().iterator(); it.hasNext();) {
            Object key = it.next();
            target.put(source.get(key), key);
        }
    }

    public static Collection filter(Collection c, Predicate p) {
        Iterator it = c.iterator();
        while (it.hasNext()) {
            if (!p.evaluate(it.next())) {
                it.remove();
            }
        }
        return c;
    }

    public static List transform(Collection c, Transformer t) {
        List result = new ArrayList(c.size());
        for (Iterator it = c.iterator(); it.hasNext();) {
            result.add(t.transform(it.next()));
        }
        return result;
    }

    public static Map getIndexMap(List list) {
        Map indexes = new HashMap();
        int index = 0;
        for (Iterator it = list.iterator(); it.hasNext();) {
            indexes.put(it.next(), new Integer(index++));
        }
        return indexes;
    }
}