org.dashbuilder.common.client.CollectionUtils Maven / Gradle / Ivy
/*
* Copyright 2014 Red Hat, Inc. and/or its affiliates.
*
* 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 org.dashbuilder.common.client;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
public class CollectionUtils {
/** Constant to avoid repeated object creation */
private static Integer INTEGER_ONE = new Integer(1);
/**
* Returns a {@link Collection} containing the intersection
* of the given {@link Collection}s.
*
* The cardinality of each element in the returned {@link Collection}
* will be equal to the minimum of the cardinality of that element
* in the two given {@link Collection}s.
*
* @param a the first collection, must not be null
* @param b the second collection, must not be null
* @return the intersection of the two collections
*/
public static Collection intersection(final Collection a, final Collection b) {
ArrayList list = new ArrayList();
Map mapa = getCardinalityMap(a);
Map mapb = getCardinalityMap(b);
Set elts = new HashSet(a);
elts.addAll(b);
Iterator it = elts.iterator();
while(it.hasNext()) {
Object obj = it.next();
for(int i=0,m=Math.min(getFreq(obj,mapa),getFreq(obj,mapb));i
* Only those elements present in the collection will appear as
* keys in the map.
*
* @param coll the collection to get the cardinality map for, must not be null
* @return the populated cardinality map
*/
public static Map getCardinalityMap(final Collection coll) {
Map count = new HashMap();
for (Iterator it = coll.iterator(); it.hasNext();) {
Object obj = it.next();
Integer c = (Integer) (count.get(obj));
if (c == null) {
count.put(obj,INTEGER_ONE);
} else {
count.put(obj,new Integer(c.intValue() + 1));
}
}
return count;
}
private static final int getFreq(final Object obj, final Map freqMap) {
Integer count = (Integer) freqMap.get(obj);
if (count != null) {
return count.intValue();
}
return 0;
}
}