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Groovy: A powerful, dynamic language for the JVM
/*
* 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
*/
public class GroovyCollections {
/**
* Finds all combinations of items from an array of lists.
*
* @param lists an array of lists
* @return a List of the combinations found
* @see #combinations(Collection)
*/
public static List combinations(Object[] lists) {
return combinations(Arrays.asList(lists));
}
/**
* Finds all combinations of items from a collection of lists.
* 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]].
*
* @param lists a Collection of lists
* @return a List of the combinations found
*/
public static List combinations(Collection lists) {
List combinations = new ArrayList();
for (Iterator outer = lists.iterator(); outer.hasNext();) {
Object candidateList = outer.next();
List list = (List) DefaultTypeTransformation.castToType(candidateList, List.class);
if (combinations.isEmpty()) {
for (int i = 0; i < list.size(); i++) {
List l = new ArrayList();
l.add(list.get(i));
combinations.add(l);
}
} else {
List savedCombinations = new ArrayList(combinations);
List newCombinations = new ArrayList();
for (Iterator inner = list.iterator(); inner.hasNext();) {
Object value = inner.next();
for (Iterator combos = savedCombinations.iterator(); combos.hasNext();) {
List oldlist = new ArrayList((List) combos.next());
oldlist.add(value);
newCombinations.add(oldlist);
}
}
combinations = newCombinations;
}
}
return combinations;
}
/**
* Transposes an array of lists.
*
* @param lists an array of lists
* @return a List of the transposed lists
* @see #transpose(Collection)
*/
public static List transpose(Object[] lists) {
return transpose(Arrays.asList(lists));
}
/**
* Transposes a collection of lists. So,
* transpose([['a', 'b'], [1, 2]])
* is [['a', 1], ['b', 2]] and.
* transpose([['a', 'b', 'c']])
* is [['a'], ['b'], ['c']] and.
*
* @param lists a Collection of lists
* @return a List of the transposed lists
*/
public static List transpose(Collection 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();) {
Object candidateList = outer.next();
List list = (List) DefaultTypeTransformation.castToType(candidateList, 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();) {
Object candidateList = outer.next();
List list = (List) DefaultTypeTransformation.castToType(candidateList, 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 Object min(Object[] 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 Object min(Collection items) {
Object answer = null;
for (Iterator iter = items.iterator(); iter.hasNext();) {
Object value = iter.next();
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 Object max(Object[] items) {
return max(Arrays.asList(items));
}
/**
* Selects the maximum value found in a collection
*
* @param items a Collection
* @return the maximum value
*/
public static Object max(Collection items) {
Object answer = null;
for (Iterator iter = items.iterator(); iter.hasNext();) {
Object value = iter.next();
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);
}
}