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/*
* Copyright (c) 2017, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package org.glassfish.jersey.internal.util.collection;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collector;
/**
* Set of convenient function regarding a collection immutability. Particularly useful in the conjunction with
* {@link java.util.stream.Stream}.
*/
public class ImmutableCollectors {
/**
* Creates a {@link Collector} of an immutable list for {@link java.util.stream.Stream#collect(Collector)}.
*
* @param type of the immutable list.
* @return collector for immutable list.
*/
public static Collector, List> toImmutableList() {
return Collector.of(ArrayList::new, List::add, (left, right) -> {
left.addAll(right);
return left;
}, Collections::unmodifiableList);
}
/**
* Creates a {@link Collector} of an immutable Set for {@link java.util.stream.Stream#collect(Collector)}.
*
* @param type of the immutable set.
* @return collector for immutable set.
*/
public static Collector, Set> toImmutableSet() {
return Collector.of(HashSet::new, Set::add, (left, right) -> {
left.addAll(right);
return left;
}, Collections::unmodifiableSet);
}
/**
* Creates a {@link Collector} of an immutable Set for {@link java.util.stream.Stream#collect(Collector)}.
*
* @param type of the immutable linked hash set.
* @return collector for immutable linked hash set.
*/
public static Collector, Set> toImmutableLinkedSet() {
return Collector.of(LinkedHashSet::new, Set::add, (left, right) -> {
left.addAll(right);
return left;
}, Collections::unmodifiableSet);
}
}