/*
 * Copyright 2018 Google LLC
 *
 * 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
 *
 *     https://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 com.google.android.gnd.util;

import com.google.common.collect.ImmutableSet;
import java8.util.stream.Collector;
import java8.util.stream.Collectors;

/**
 * Custom collector for compatibility between {@link Collector} compat class and Guava {@link
 * ImmutableSet}.
 */
public abstract class ImmutableSetCollector {
  /** Do not instantiate. */
  private ImmutableSetCollector() {}

  private static final Collector<Object, ?, ImmutableSet<Object>> TO_IMMUTABLE_SET =
      Collectors.of(
          ImmutableSet::builder,
          ImmutableSet.Builder::add,
          (a, b) -> {
            throw new UnsupportedOperationException();
          },
          ImmutableSet.Builder::build);

  /** Returns a {@link Collector} that accumulates the input elements into a new ImmutableSet. */
  public static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return (Collector) TO_IMMUTABLE_SET;
  }
}

/*
 * Copyright 2019 Google LLC
 *
 * 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
 *
 *     https://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 com.google.android.gnd.util;

import com.google.common.collect.ImmutableSet;
import java8.util.stream.Collector;
import java8.util.stream.Collectors;

/**
 * Custom collector for compatibility between {@link Collector} compat class and Guava {@link
 * ImmutableSet}.
 */
public abstract class ImmutableSetCollector {
  /** Do not instantiate. */
  private ImmutableSetCollector() {}

  private static final Collector<Object, ?, ImmutableSet<Object>> TO_IMMUTABLE_SET =
      Collectors.of(
          ImmutableSet::builder,
          ImmutableSet.Builder::add,
          (a, b) -> {
            throw new UnsupportedOperationException();
          },
          ImmutableSet.Builder::build);

  /** Returns a {@link Collector} that accumulates the input elements into a new ImmutableSet. */
  public static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return (Collector) TO_IMMUTABLE_SET;
  }
}

Fix copyright on new file