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Groovy: A powerful, dynamic language for the JVM
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 groovy.util;
import org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation;
import org.codehaus.groovy.runtime.ScriptBytecodeAdapter;
import org.codehaus.groovy.runtime.DefaultGroovyMethods;
import java.util.*;
/**
* A Collections utility class
*
* @author Paul King
* @author Jim White
*/
public class GroovyCollections {
/**
* Finds all combinations of items from the given collections.
*
* @param collections the given collections
* @return a List of the combinations found
* @see #combinations(Collection)
*/
public static List combinations(Object[] collections) {
return combinations((Iterable)Arrays.asList(collections));
}
/**
* Finds all non-null subsequences of a list.
* E.g. subsequences([1, 2, 3]) would be:
* [[1, 2, 3], [1, 3], [2, 3], [1, 2], [1], [2], [3]]
*
* @param items the List of items
* @return the subsequences from items
*/
public static Set> subsequences(List items) {
// items.inject([]){ ss, h -> ss.collect { it + [h] } + ss + [[h]] }
Set> ans = new HashSet>();
for (T h : items) {
Set> next = new HashSet>();
for (List it : ans) {
List sublist = new ArrayList(it);
sublist.add(h);
next.add(sublist);
}
next.addAll(ans);
List hlist = new ArrayList();
hlist.add(h);
next.add(hlist);
ans = next;
}
return ans;
}
/**
* @param collections the given collections
* @deprecated use combinations(Iterable)
*/
@Deprecated
public static List combinations(Collection collections) {
return combinations((Iterable)collections);
}
/**
* Finds all combinations of items from the given Iterable aggregate of collections.
* So, combinations([[true, false], [true, false]])
* is [[true, true], [false, true], [true, false], [false, false]]
* and combinations([['a', 'b'],[1, 2, 3]])
* is [['a', 1], ['b', 1], ['a', 2], ['b', 2], ['a', 3], ['b', 3]].
* If a non-collection item is given, it is treated as a singleton collection,
* i.e. combinations([[1, 2], 'x']) is [[1, 'x'], [2, 'x']].
*
* @param collections the Iterable of given collections
* @return a List of the combinations found
* @since 2.2.0
*/
public static List combinations(Iterable collections) {
List collectedCombos = new ArrayList();
for (Object collection : collections) {
Iterable items = DefaultTypeTransformation.asCollection(collection);
if (collectedCombos.isEmpty()) {
for (Object item : items) {
List l = new ArrayList();
l.add(item);
collectedCombos.add(l);
}
} else {
List savedCombos = new ArrayList(collectedCombos);
List newCombos = new ArrayList();
for (Object value : items) {
for (Object savedCombo : savedCombos) {
List oldList = new ArrayList((List) savedCombo);
oldList.add(value);
newCombos.add(oldList);
}
}
collectedCombos = newCombos;
}
}
return collectedCombos;
}
/**
* Transposes an array of lists.
*
* @param lists the given lists
* @return a List of the transposed lists
* @see #transpose(List)
*/
public static List transpose(Object[] lists) {
return transpose(Arrays.asList(lists));
}
/**
* Transposes the given lists.
* So, transpose([['a', 'b'], [1, 2]])
* is [['a', 1], ['b', 2]] and
* transpose([['a', 'b', 'c']])
* is [['a'], ['b'], ['c']].
*
* @param lists the given lists
* @return a List of the transposed lists
*/
public static List transpose(List lists) {
List result = new ArrayList();
if (lists.isEmpty() || lists.isEmpty()) return result;
int minSize = Integer.MAX_VALUE;
for (Object listLike : lists) {
List list = (List) DefaultTypeTransformation.castToType(listLike, List.class);
if (list.size() < minSize) minSize = list.size();
}
if (minSize == 0) return result;
for (int i = 0; i < minSize; i++) {
result.add(new ArrayList());
}
for (Object listLike : lists) {
List list = (List) DefaultTypeTransformation.castToType(listLike, List.class);
for (int i = 0; i < minSize; i++) {
List resultList = (List) result.get(i);
resultList.add(list.get(i));
}
}
return result;
}
/**
* Selects the minimum value found in an array of items, so
* min([2, 4, 6] as Object[]) == 2.
*
* @param items an array of items
* @return the minimum value
*/
public static T min(T[] items) {
return min((Iterable)Arrays.asList(items));
}
/**
* @deprecated use min(Iterable)
*/
@Deprecated
public static T min(Collection items) {
return min((Iterable)items);
}
/**
* Selects the minimum value found in an Iterable of items.
*
* @param items an Iterable
* @return the minimum value
* @since 2.2.0
*/
public static T min(Iterable items) {
T answer = null;
for (T value : items) {
if (value != null) {
if (answer == null || ScriptBytecodeAdapter.compareLessThan(value, answer)) {
answer = value;
}
}
}
return answer;
}
/**
* Selects the maximum value found in an array of items, so
* min([2, 4, 6] as Object[]) == 6.
*
* @param items an array of items
* @return the maximum value
*/
public static T max(T[] items) {
return max((Iterable)Arrays.asList(items));
}
/**
* @deprecated use max(Iterable)
*/
@Deprecated
public static T max(Collection items) {
return max((Iterable)items);
}
/**
* Selects the maximum value found in an Iterable.
*
* @param items a Collection
* @return the maximum value
* @since 2.2.0
*/
public static T max(Iterable items) {
T answer = null;
for (T value : items) {
if (value != null) {
if (answer == null || ScriptBytecodeAdapter.compareGreaterThan(value, answer)) {
answer = value;
}
}
}
return answer;
}
/**
* Sums all the items from an array of items.
*
* @param items an array of items
* @return the sum of the items
*/
public static Object sum(Object[] items) {
return sum((Iterable)Arrays.asList(items));
}
/**
* @deprecated use sum(Iterable)
*/
@Deprecated
public static Object sum(Collection items) {
return sum((Iterable)items);
}
/**
* Sums all the given items.
*
* @param items an Iterable of items
* @return the sum of the item
* @since 2.2.0
*/
public static Object sum(Iterable items) {
return DefaultGroovyMethods.sum(items);
}
}