All Downloads are FREE. Search and download functionalities are using the official Maven repository.

jersey.repackaged.com.google.common.collect.Collections2 Maven / Gradle / Ivy

The newest version!
/*
 * Copyright (C) 2008 The Guava 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 jersey.repackaged.com.google.common.collect;

import static jersey.repackaged.com.google.common.base.Preconditions.checkArgument;
import static jersey.repackaged.com.google.common.base.Preconditions.checkNotNull;
import static jersey.repackaged.com.google.common.base.Predicates.and;
import static jersey.repackaged.com.google.common.base.Predicates.in;
import static jersey.repackaged.com.google.common.base.Predicates.not;
import static jersey.repackaged.com.google.common.collect.CollectPreconditions.checkNonnegative;
import static jersey.repackaged.com.google.common.math.LongMath.binomial;

import jersey.repackaged.com.google.common.annotations.Beta;
import jersey.repackaged.com.google.common.annotations.GwtCompatible;
import jersey.repackaged.com.google.common.base.Function;
import jersey.repackaged.com.google.common.base.Joiner;
import jersey.repackaged.com.google.common.base.Predicate;
import jersey.repackaged.com.google.common.base.Predicates;
import jersey.repackaged.com.google.common.math.IntMath;
import jersey.repackaged.com.google.common.primitives.Ints;

import java.util.AbstractCollection;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;

import javax.annotation.Nullable;

/**
 * Provides static methods for working with {@code Collection} instances.
 *
 * @author Chris Povirk
 * @author Mike Bostock
 * @author Jared Levy
 * @since 2.0 (imported from Google Collections Library)
 */
@GwtCompatible
public final class Collections2 {
  private Collections2() {}

  /**
   * Returns the elements of {@code unfiltered} that satisfy a predicate. The
   * returned collection is a live view of {@code unfiltered}; changes to one
   * affect the other.
   *
   * 

The resulting collection's iterator does not support {@code remove()}, * but all other collection methods are supported. When given an element that * doesn't satisfy the predicate, the collection's {@code add()} and {@code * addAll()} methods throw an {@link IllegalArgumentException}. When methods * such as {@code removeAll()} and {@code clear()} are called on the filtered * collection, only elements that satisfy the filter will be removed from the * underlying collection. * *

The returned collection isn't threadsafe or serializable, even if * {@code unfiltered} is. * *

Many of the filtered collection's methods, such as {@code size()}, * iterate across every element in the underlying collection and determine * which elements satisfy the filter. When a live view is not needed, * it may be faster to copy {@code Iterables.filter(unfiltered, predicate)} * and use the copy. * *

Warning: {@code predicate} must be consistent with equals, * as documented at {@link Predicate#apply}. Do not provide a predicate such * as {@code Predicates.instanceOf(ArrayList.class)}, which is inconsistent * with equals. (See {@link Iterables#filter(Iterable, Class)} for related * functionality.) */ // TODO(kevinb): how can we omit that Iterables link when building gwt // javadoc? public static Collection filter( Collection unfiltered, Predicate predicate) { if (unfiltered instanceof FilteredCollection) { // Support clear(), removeAll(), and retainAll() when filtering a filtered // collection. return ((FilteredCollection) unfiltered).createCombined(predicate); } return new FilteredCollection( checkNotNull(unfiltered), checkNotNull(predicate)); } /** * Delegates to {@link Collection#contains}. Returns {@code false} if the * {@code contains} method throws a {@code ClassCastException} or * {@code NullPointerException}. */ static boolean safeContains( Collection collection, @Nullable Object object) { checkNotNull(collection); try { return collection.contains(object); } catch (ClassCastException e) { return false; } catch (NullPointerException e) { return false; } } /** * Delegates to {@link Collection#remove}. Returns {@code false} if the * {@code remove} method throws a {@code ClassCastException} or * {@code NullPointerException}. */ static boolean safeRemove(Collection collection, @Nullable Object object) { checkNotNull(collection); try { return collection.remove(object); } catch (ClassCastException e) { return false; } catch (NullPointerException e) { return false; } } static class FilteredCollection extends AbstractCollection { final Collection unfiltered; final Predicate predicate; FilteredCollection(Collection unfiltered, Predicate predicate) { this.unfiltered = unfiltered; this.predicate = predicate; } FilteredCollection createCombined(Predicate newPredicate) { return new FilteredCollection(unfiltered, Predicates.and(predicate, newPredicate)); // . above needed to compile in JDK 5 } @Override public boolean add(E element) { checkArgument(predicate.apply(element)); return unfiltered.add(element); } @Override public boolean addAll(Collection collection) { for (E element : collection) { checkArgument(predicate.apply(element)); } return unfiltered.addAll(collection); } @Override public void clear() { Iterables.removeIf(unfiltered, predicate); } @Override public boolean contains(@Nullable Object element) { if (safeContains(unfiltered, element)) { @SuppressWarnings("unchecked") // element is in unfiltered, so it must be an E E e = (E) element; return predicate.apply(e); } return false; } @Override public boolean containsAll(Collection collection) { return containsAllImpl(this, collection); } @Override public boolean isEmpty() { return !Iterables.any(unfiltered, predicate); } @Override public Iterator iterator() { return Iterators.filter(unfiltered.iterator(), predicate); } @Override public boolean remove(Object element) { return contains(element) && unfiltered.remove(element); } @Override public boolean removeAll(final Collection collection) { return Iterables.removeIf(unfiltered, and(predicate, in(collection))); } @Override public boolean retainAll(final Collection collection) { return Iterables.removeIf(unfiltered, and(predicate, not(in(collection)))); } @Override public int size() { return Iterators.size(iterator()); } @Override public Object[] toArray() { // creating an ArrayList so filtering happens once return Lists.newArrayList(iterator()).toArray(); } @Override public T[] toArray(T[] array) { return Lists.newArrayList(iterator()).toArray(array); } } /** * Returns a collection that applies {@code function} to each element of * {@code fromCollection}. The returned collection is a live view of {@code * fromCollection}; changes to one affect the other. * *

The returned collection's {@code add()} and {@code addAll()} methods * throw an {@link UnsupportedOperationException}. All other collection * methods are supported, as long as {@code fromCollection} supports them. * *

The returned collection isn't threadsafe or serializable, even if * {@code fromCollection} is. * *

When a live view is not needed, it may be faster to copy the * transformed collection and use the copy. * *

If the input {@code Collection} is known to be a {@code List}, consider * {@link Lists#transform}. If only an {@code Iterable} is available, use * {@link Iterables#transform}. */ public static Collection transform(Collection fromCollection, Function function) { return new TransformedCollection(fromCollection, function); } static class TransformedCollection extends AbstractCollection { final Collection fromCollection; final Function function; TransformedCollection(Collection fromCollection, Function function) { this.fromCollection = checkNotNull(fromCollection); this.function = checkNotNull(function); } @Override public void clear() { fromCollection.clear(); } @Override public boolean isEmpty() { return fromCollection.isEmpty(); } @Override public Iterator iterator() { return Iterators.transform(fromCollection.iterator(), function); } @Override public int size() { return fromCollection.size(); } } /** * Returns {@code true} if the collection {@code self} contains all of the * elements in the collection {@code c}. * *

This method iterates over the specified collection {@code c}, checking * each element returned by the iterator in turn to see if it is contained in * the specified collection {@code self}. If all elements are so contained, * {@code true} is returned, otherwise {@code false}. * * @param self a collection which might contain all elements in {@code c} * @param c a collection whose elements might be contained by {@code self} */ static boolean containsAllImpl(Collection self, Collection c) { return Iterables.all(c, Predicates.in(self)); } /** * An implementation of {@link Collection#toString()}. */ static String toStringImpl(final Collection collection) { StringBuilder sb = newStringBuilderForCollection(collection.size()).append('['); STANDARD_JOINER.appendTo( sb, Iterables.transform(collection, new Function() { @Override public Object apply(Object input) { return input == collection ? "(this Collection)" : input; } })); return sb.append(']').toString(); } /** * Returns best-effort-sized StringBuilder based on the given collection size. */ static StringBuilder newStringBuilderForCollection(int size) { checkNonnegative(size, "size"); return new StringBuilder((int) Math.min(size * 8L, Ints.MAX_POWER_OF_TWO)); } /** * Used to avoid http://bugs.sun.com/view_bug.do?bug_id=6558557 */ static Collection cast(Iterable iterable) { return (Collection) iterable; } static final Joiner STANDARD_JOINER = Joiner.on(", ").useForNull("null"); /** * Returns a {@link Collection} of all the permutations of the specified * {@link Iterable}. * *

Notes: This is an implementation of the algorithm for * Lexicographical Permutations Generation, described in Knuth's "The Art of * Computer Programming", Volume 4, Chapter 7, Section 7.2.1.2. The * iteration order follows the lexicographical order. This means that * the first permutation will be in ascending order, and the last will be in * descending order. * *

Duplicate elements are considered equal. For example, the list [1, 1] * will have only one permutation, instead of two. This is why the elements * have to implement {@link Comparable}. * *

An empty iterable has only one permutation, which is an empty list. * *

This method is equivalent to * {@code Collections2.orderedPermutations(list, Ordering.natural())}. * * @param elements the original iterable whose elements have to be permuted. * @return an immutable {@link Collection} containing all the different * permutations of the original iterable. * @throws NullPointerException if the specified iterable is null or has any * null elements. * @since 12.0 */ @Beta public static > Collection> orderedPermutations(Iterable elements) { return orderedPermutations(elements, Ordering.natural()); } /** * Returns a {@link Collection} of all the permutations of the specified * {@link Iterable} using the specified {@link Comparator} for establishing * the lexicographical ordering. * *

Examples:

   {@code
   *
   *   for (List perm : orderedPermutations(asList("b", "c", "a"))) {
   *     println(perm);
   *   }
   *   // -> ["a", "b", "c"]
   *   // -> ["a", "c", "b"]
   *   // -> ["b", "a", "c"]
   *   // -> ["b", "c", "a"]
   *   // -> ["c", "a", "b"]
   *   // -> ["c", "b", "a"]
   *
   *   for (List perm : orderedPermutations(asList(1, 2, 2, 1))) {
   *     println(perm);
   *   }
   *   // -> [1, 1, 2, 2]
   *   // -> [1, 2, 1, 2]
   *   // -> [1, 2, 2, 1]
   *   // -> [2, 1, 1, 2]
   *   // -> [2, 1, 2, 1]
   *   // -> [2, 2, 1, 1]}
* *

Notes: This is an implementation of the algorithm for * Lexicographical Permutations Generation, described in Knuth's "The Art of * Computer Programming", Volume 4, Chapter 7, Section 7.2.1.2. The * iteration order follows the lexicographical order. This means that * the first permutation will be in ascending order, and the last will be in * descending order. * *

Elements that compare equal are considered equal and no new permutations * are created by swapping them. * *

An empty iterable has only one permutation, which is an empty list. * * @param elements the original iterable whose elements have to be permuted. * @param comparator a comparator for the iterable's elements. * @return an immutable {@link Collection} containing all the different * permutations of the original iterable. * @throws NullPointerException If the specified iterable is null, has any * null elements, or if the specified comparator is null. * @since 12.0 */ @Beta public static Collection> orderedPermutations( Iterable elements, Comparator comparator) { return new OrderedPermutationCollection(elements, comparator); } private static final class OrderedPermutationCollection extends AbstractCollection> { final ImmutableList inputList; final Comparator comparator; final int size; OrderedPermutationCollection(Iterable input, Comparator comparator) { this.inputList = Ordering.from(comparator).immutableSortedCopy(input); this.comparator = comparator; this.size = calculateSize(inputList, comparator); } /** * The number of permutations with repeated elements is calculated as * follows: *

    *
  • For an empty list, it is 1 (base case).
  • *
  • When r numbers are added to a list of n-r elements, the number of * permutations is increased by a factor of (n choose r).
  • *
*/ private static int calculateSize( List sortedInputList, Comparator comparator) { long permutations = 1; int n = 1; int r = 1; while (n < sortedInputList.size()) { int comparison = comparator.compare( sortedInputList.get(n - 1), sortedInputList.get(n)); if (comparison < 0) { // We move to the next non-repeated element. permutations *= binomial(n, r); r = 0; if (!isPositiveInt(permutations)) { return Integer.MAX_VALUE; } } n++; r++; } permutations *= binomial(n, r); if (!isPositiveInt(permutations)) { return Integer.MAX_VALUE; } return (int) permutations; } @Override public int size() { return size; } @Override public boolean isEmpty() { return false; } @Override public Iterator> iterator() { return new OrderedPermutationIterator(inputList, comparator); } @Override public boolean contains(@Nullable Object obj) { if (obj instanceof List) { List list = (List) obj; return isPermutation(inputList, list); } return false; } @Override public String toString() { return "orderedPermutationCollection(" + inputList + ")"; } } private static final class OrderedPermutationIterator extends AbstractIterator> { List nextPermutation; final Comparator comparator; OrderedPermutationIterator(List list, Comparator comparator) { this.nextPermutation = Lists.newArrayList(list); this.comparator = comparator; } @Override protected List computeNext() { if (nextPermutation == null) { return endOfData(); } ImmutableList next = ImmutableList.copyOf(nextPermutation); calculateNextPermutation(); return next; } void calculateNextPermutation() { int j = findNextJ(); if (j == -1) { nextPermutation = null; return; } int l = findNextL(j); Collections.swap(nextPermutation, j, l); int n = nextPermutation.size(); Collections.reverse(nextPermutation.subList(j + 1, n)); } int findNextJ() { for (int k = nextPermutation.size() - 2; k >= 0; k--) { if (comparator.compare(nextPermutation.get(k), nextPermutation.get(k + 1)) < 0) { return k; } } return -1; } int findNextL(int j) { E ak = nextPermutation.get(j); for (int l = nextPermutation.size() - 1; l > j; l--) { if (comparator.compare(ak, nextPermutation.get(l)) < 0) { return l; } } throw new AssertionError("this statement should be unreachable"); } } /** * Returns a {@link Collection} of all the permutations of the specified * {@link Collection}. * *

Notes: This is an implementation of the Plain Changes algorithm * for permutations generation, described in Knuth's "The Art of Computer * Programming", Volume 4, Chapter 7, Section 7.2.1.2. * *

If the input list contains equal elements, some of the generated * permutations will be equal. * *

An empty collection has only one permutation, which is an empty list. * * @param elements the original collection whose elements have to be permuted. * @return an immutable {@link Collection} containing all the different * permutations of the original collection. * @throws NullPointerException if the specified collection is null or has any * null elements. * @since 12.0 */ @Beta public static Collection> permutations( Collection elements) { return new PermutationCollection(ImmutableList.copyOf(elements)); } private static final class PermutationCollection extends AbstractCollection> { final ImmutableList inputList; PermutationCollection(ImmutableList input) { this.inputList = input; } @Override public int size() { return IntMath.factorial(inputList.size()); } @Override public boolean isEmpty() { return false; } @Override public Iterator> iterator() { return new PermutationIterator(inputList); } @Override public boolean contains(@Nullable Object obj) { if (obj instanceof List) { List list = (List) obj; return isPermutation(inputList, list); } return false; } @Override public String toString() { return "permutations(" + inputList + ")"; } } private static class PermutationIterator extends AbstractIterator> { final List list; final int[] c; final int[] o; int j; PermutationIterator(List list) { this.list = new ArrayList(list); int n = list.size(); c = new int[n]; o = new int[n]; Arrays.fill(c, 0); Arrays.fill(o, 1); j = Integer.MAX_VALUE; } @Override protected List computeNext() { if (j <= 0) { return endOfData(); } ImmutableList next = ImmutableList.copyOf(list); calculateNextPermutation(); return next; } void calculateNextPermutation() { j = list.size() - 1; int s = 0; // Handle the special case of an empty list. Skip the calculation of the // next permutation. if (j == -1) { return; } while (true) { int q = c[j] + o[j]; if (q < 0) { switchDirection(); continue; } if (q == j + 1) { if (j == 0) { break; } s++; switchDirection(); continue; } Collections.swap(list, j - c[j] + s, j - q + s); c[j] = q; break; } } void switchDirection() { o[j] = -o[j]; j--; } } /** * Returns {@code true} if the second list is a permutation of the first. */ private static boolean isPermutation(List first, List second) { if (first.size() != second.size()) { return false; } Multiset firstMultiset = HashMultiset.create(first); Multiset secondMultiset = HashMultiset.create(second); return firstMultiset.equals(secondMultiset); } private static boolean isPositiveInt(long n) { return n >= 0 && n <= Integer.MAX_VALUE; } }





© 2015 - 2024 Weber Informatics LLC | Privacy Policy