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/*
* 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.cassandra.utils;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collector;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
/**
* Some extra Collector implementations.
*
* Named Collectors3 just in case Guava ever makes a Collectors2
*/
public class Collectors3
{
private static final Collector.Characteristics[] LIST_CHARACTERISTICS = new Collector.Characteristics[]{};
public static Collector> toImmutableList()
{
return Collector.of(ImmutableList.Builder::new,
ImmutableList.Builder::add,
(l, r) -> l.addAll(r.build()),
ImmutableList.Builder::build,
LIST_CHARACTERISTICS);
}
private static final Collector.Characteristics[] SET_CHARACTERISTICS = new Collector.Characteristics[]{ Collector.Characteristics.UNORDERED };
public static Collector> toImmutableSet()
{
return Collector.of(ImmutableSet.Builder::new,
ImmutableSet.Builder::add,
(l, r) -> l.addAll(r.build()),
ImmutableSet.Builder::build,
SET_CHARACTERISTICS);
}
private static final Collector.Characteristics[] MAP_CHARACTERISTICS = new Collector.Characteristics[]{ Collector.Characteristics.UNORDERED };
public static Collector, ?, ImmutableMap> toImmutableMap()
{
return Collector.of(ImmutableMap.Builder::new,
ImmutableMap.Builder::put,
(l, r) -> l.putAll(r.build()),
ImmutableMap.Builder::build,
MAP_CHARACTERISTICS);
}
public static Collector> toImmutableMap(Function keyMapper, Function valueMapper)
{
return Collector.of(ImmutableMap.Builder::new,
(b, t) -> b.put(keyMapper.apply(t), valueMapper.apply(t)),
(l, r) -> l.putAll(r.build()),
ImmutableMap.Builder::build,
MAP_CHARACTERISTICS);
}
}