groovy.util.GroovyCollections Maven / Gradle / Ivy
/*
* Copyright 2003-2007 the original author or authors.
*
* 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 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(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;
}
/**
* Finds all combinations of items from the given 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 given collections
* @return a List of the combinations found
*/
public static List combinations(Collection collections) {
List collectedCombos = new ArrayList();
for (Iterator outer = collections.iterator(); outer.hasNext();) {
Collection items = DefaultTypeTransformation.asCollection(outer.next());
if (collectedCombos.isEmpty()) {
for (Iterator iterator = items.iterator(); iterator.hasNext();) {
List l = new ArrayList();
l.add(iterator.next());
collectedCombos.add(l);
}
} else {
List savedCombos = new ArrayList(collectedCombos);
List newCombos = new ArrayList();
for (Iterator inner = items.iterator(); inner.hasNext();) {
Object value = inner.next();
for (Iterator combos = savedCombos.iterator(); combos.hasNext();) {
List oldlist = new ArrayList((List) combos.next());
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.size() == 0) return result;
int minSize = Integer.MAX_VALUE;
for (Iterator outer = lists.iterator(); outer.hasNext();) {
List list = (List) DefaultTypeTransformation.castToType(outer.next(), 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 (Iterator outer = lists.iterator(); outer.hasNext();) {
List list = (List) DefaultTypeTransformation.castToType(outer.next(), 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(Arrays.asList(items));
}
/**
* Selects the minimum value found in a collection of items.
*
* @param items a Collection
* @return the minimum value
*/
public static T min(Collection 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(Arrays.asList(items));
}
/**
* Selects the maximum value found in a collection
*
* @param items a Collection
* @return the maximum value
*/
public static T max(Collection 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 DefaultGroovyMethods.sum(Arrays.asList(items));
}
/**
* Sums all the items from a collection of items.
*
* @param items a collection of items
* @return the sum of the items
*/
public static Object sum(Collection items) {
return DefaultGroovyMethods.sum(items);
}
}
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