/*
* 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.
DefaultGroovyMethods;
import org.codehaus.groovy.runtime.
ScriptBytecodeAdapter;
import org.codehaus.groovy.runtime.typehandling.
DefaultTypeTransformation;
import java.util.
ArrayList;
import java.util.
Arrays;
import java.util.
Collection;
import java.util.
HashSet;
import java.util.
List;
import java.util.
Set;
/**
* 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. <code>subsequences([1, 2, 3])</code> 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 <T>
Set<
List<T>>
subsequences(
List<T>
items) {
// items.inject([]){ ss, h -> ss.collect { it + [h] } + ss + [[h]] }
Set<
List<T>>
ans = new
HashSet<
List<T>>();
for (T
h :
items) {
Set<
List<T>>
next = new
HashSet<
List<T>>();
for (
List<T>
it :
ans) {
List<T>
sublist = new
ArrayList<T>(
it);
sublist.
add(
h);
next.
add(
sublist);
}
next.
addAll(
ans);
List<T>
hlist = new
ArrayList<T>();
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, <code>combinations([[true, false], [true, false]])</code>
* is <code>[[true, true], [false, true], [true, false], [false, false]]</code>
* and <code>combinations([['a', 'b'],[1, 2, 3]])</code>
* is <code>[['a', 1], ['b', 1], ['a', 2], ['b', 2], ['a', 3], ['b', 3]]</code>.
* If a non-collection item is given, it is treated as a singleton collection,
* i.e. <code>combinations([[1, 2], 'x'])</code> is <code>[[1, 'x'], [2, 'x']]</code>.
* If an empty collection is found within the given collections, the result will be an empty list.
*
* @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;
}
if (
collectedCombos.
isEmpty())
break;
}
return
collectedCombos;
}
public static <T>
List<
List<T>>
inits(
Iterable<T>
collections) {
List<T>
copy =
DefaultGroovyMethods.
toList(
collections);
List<
List<T>>
result = new
ArrayList<
List<T>>();
for (int
i =
copy.
size();
i >= 0;
i--) {
List<T>
next =
copy.
subList(0,
i);
result.
add(
next);
}
return
result;
}
public static <T>
List<
List<T>>
tails(
Iterable<T>
collections) {
List<T>
copy =
DefaultGroovyMethods.
toList(
collections);
List<
List<T>>
result = new
ArrayList<
List<T>>();
for (int
i = 0;
i <=
copy.
size();
i++) {
List<T>
next =
copy.
subList(
i,
copy.
size());
result.
add(
next);
}
return
result;
}
/**
* 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, <code>transpose([['a', 'b'], [1, 2]])</code>
* is <code>[['a', 1], ['b', 2]]</code> and
* <code>transpose([['a', 'b', 'c']])</code>
* is <code>[['a'], ['b'], ['c']]</code>.
*
* @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()) 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> T
min(T[]
items) {
return
min((
Iterable<T>)
Arrays.
asList(
items));
}
/**
* @deprecated use min(Iterable)
*/
@
Deprecated
public static <T> T
min(
Collection<T>
items) {
return
min((
Iterable<T>)
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> T
min(
Iterable<T>
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> T
max(T[]
items) {
return
max((
Iterable<T>)
Arrays.
asList(
items));
}
/**
* @deprecated use max(Iterable)
*/
@
Deprecated
public static <T> T
max(
Collection<T>
items) {
return
max((
Iterable<T>)
items);
}
/**
* Selects the maximum value found in an Iterable.
*
* @param items a Collection
* @return the maximum value
* @since 2.2.0
*/
public static <T> T
max(
Iterable<T>
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);
}
}