CollectionUtil.java
/*
* Copyright 2016 Red Hat, Inc. and/or its affiliates
* and other contributors as indicated by the @author tags.
*
* 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.keycloak.common.util;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;
/**
* @author <a href="mailto:jeroen.rosenberg@gmail.com">Jeroen Rosenberg</a>
*/
public class CollectionUtil {
public static String join(Collection<String> strings) {
return join(strings, ", ");
}
public static String join(Collection<String> strings, String separator) {
Iterator<String> iter = strings.iterator();
StringBuilder sb = new StringBuilder();
if(iter.hasNext()){
sb.append(iter.next());
while(iter.hasNext()){
sb.append(separator).append(iter.next());
}
}
return sb.toString();
}
// Return true if all items from col1 are in col2 and viceversa. Order is not taken into account
public static <T> boolean collectionEquals(Collection<T> col1, Collection<T> col2) {
if (col1.size()!=col2.size()) {
return false;
}
Map<T, Integer> countMap = new HashMap<>();
for(T o : col1) {
Integer v = countMap.get(o);
countMap.put(o, v==null ? 1 : v+1);
}
for(T o : col2) {
Integer v = countMap.get(o);
if (v==null) {
return false;
}
countMap.put(o, v-1);
}
for(Integer count : countMap.values()) {
if (count!=0) {
return false;
}
}
return true;
}
public static boolean isEmpty(Collection<?> collection) {
return collection == null || collection.isEmpty();
}
public static boolean isNotEmpty(Collection<?> collection) {
return !isEmpty(collection);
}
public static <T> Set<T> intersection(Collection<T> col1, Collection<T> col2) {
if (isEmpty(col1) || isEmpty(col2)) return Collections.emptySet();
final Collection<T> iteratorCollection = col1.size() <= col2.size() ? col1 : col2;
final Collection<T> searchCollection = iteratorCollection.equals(col1) ? col2 : col1;
return iteratorCollection.stream()
.filter(searchCollection::contains)
.collect(Collectors.toSet());
}
}