CollectionUtils.java
/*
* 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 org.apache.tools.ant.util;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Dictionary;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.Vector;
import java.util.stream.Collectors;
// CheckStyle:HideUtilityClassConstructorCheck OFF - bc
/**
* A set of helper methods related to collection manipulation.
*
* @since Ant 1.5
*/
public class CollectionUtils {
@SuppressWarnings("rawtypes")
@Deprecated
public static final List EMPTY_LIST = Collections.EMPTY_LIST; //NOSONAR
/**
* Please use Vector.equals() or List.equals().
* @param v1 the first vector.
* @param v2 the second vector.
* @return true if the vectors are equal.
* @since Ant 1.5
* @deprecated since 1.6.x.
*/
public static boolean equals(Vector<?> v1, Vector<?> v2) {
return Objects.equals(v1, v2);
}
/**
* Dictionary does not have an equals.
* Please use Map.equals().
*
* <p>Follows the equals contract of Java 2's Map.</p>
* @param d1 the first directory.
* @param d2 the second directory.
* @return true if the directories are equal.
* @since Ant 1.5
* @deprecated since 1.6.x.
*/
public static boolean equals(Dictionary<?, ?> d1, Dictionary<?, ?> d2) {
if (d1 == d2) {
return true;
}
if (d1 == null || d2 == null) {
return false;
}
if (d1.size() != d2.size()) {
return false;
}
Enumeration<?> e1 = d1.keys();
while (e1.hasMoreElements()) {
Object key = e1.nextElement();
Object value1 = d1.get(key);
Object value2 = d2.get(key);
if (value2 == null || !value1.equals(value2)) {
return false;
}
}
// don't need the opposite check as the Dictionaries have the
// same size, so we've also covered all keys of d2 already.
return true;
}
/**
* Creates a comma separated list of all values held in the given
* collection.
*
* @param c collection to transform
* @return string representation of the collection
* @since Ant 1.8.0
*/
public static String flattenToString(Collection<?> c) {
return c.stream().map(String::valueOf).collect(Collectors.joining(","));
}
/**
* Dictionary does not know the putAll method. Please use Map.putAll().
* @param m1 the to directory.
* @param m2 the from directory.
* @param <K> type of the key
* @param <V> type of the value
* @since Ant 1.6
* @deprecated since 1.6.x.
*/
public static <K, V> void putAll(Dictionary<? super K, ? super V> m1,
Dictionary<? extends K, ? extends V> m2) {
for (Enumeration<? extends K> it = m2.keys(); it.hasMoreElements();) {
K key = it.nextElement();
m1.put(key, m2.get(key));
}
}
/**
* An empty enumeration.
* @since Ant 1.6
*/
@Deprecated
public static final class EmptyEnumeration<E> implements Enumeration<E> {
/**
* @return false always.
*/
@Override
public boolean hasMoreElements() {
return false;
}
/**
* @return nothing.
* @throws NoSuchElementException always.
*/
@Override
public E nextElement() throws NoSuchElementException {
throw new NoSuchElementException();
}
}
/**
* Append one enumeration to another.
* Elements are evaluated lazily.
* @param e1 the first enumeration.
* @param e2 the subsequent enumeration.
* @param <E> element type
* @return an enumeration representing e1 followed by e2.
* @since Ant 1.6.3
*/
public static <E> Enumeration<E> append(Enumeration<E> e1, Enumeration<E> e2) {
return new CompoundEnumeration<>(e1, e2);
}
/**
* Adapt the specified Iterator to the Enumeration interface.
* @param iter the Iterator to adapt.
* @param <E> element type
* @return an Enumeration.
*/
public static <E> Enumeration<E> asEnumeration(final Iterator<E> iter) {
return new Enumeration<E>() {
@Override
public boolean hasMoreElements() {
return iter.hasNext();
}
@Override
public E nextElement() {
return iter.next();
}
};
}
/**
* Adapt the specified Enumeration to the Iterator interface.
* @param e the Enumeration to adapt.
* @param <E> element type
* @return an Iterator.
*/
public static <E> Iterator<E> asIterator(final Enumeration<E> e) {
return new Iterator<E>() {
@Override
public boolean hasNext() {
return e.hasMoreElements();
}
@Override
public E next() {
return e.nextElement();
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
/**
* Returns a collection containing all elements of the iterator.
*
* @param iter the Iterator to convert
* @param <T> element type
* @return the collection
* @since Ant 1.8.0
*/
public static <T> Collection<T> asCollection(final Iterator<? extends T> iter) {
List<T> l = new ArrayList<>();
iter.forEachRemaining(l::add);
return l;
}
private static final class CompoundEnumeration<E> implements Enumeration<E> {
private final Enumeration<E> e1, e2;
public CompoundEnumeration(Enumeration<E> e1, Enumeration<E> e2) {
this.e1 = e1;
this.e2 = e2;
}
@Override
public boolean hasMoreElements() {
return e1.hasMoreElements() || e2.hasMoreElements();
}
@Override
public E nextElement() throws NoSuchElementException {
if (e1.hasMoreElements()) {
return e1.nextElement();
}
return e2.nextElement();
}
}
/**
* Counts how often the given Object occurs in the given
* collection using equals() for comparison.
*
* @param c collection in which to search
* @param o object to search
* @return frequency
* @since Ant 1.8.0
*/
@Deprecated
public static int frequency(Collection<?> c, Object o) {
return Collections.frequency(c, o);
}
private CollectionUtils() {
}
}