Java tutorial
/* * Copyright 2013 serso aka se.solovyev * * 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 org.solovyev.common.collections.multimap; import com.google.common.collect.Iterables; import javax.annotation.Nonnull; import javax.annotation.Nullable; import java.util.List; public final class ObjectAddedUpdater<V> implements ThreadSafeMultimap.ListUpdater<V> { @Nonnull private final V newObject; public ObjectAddedUpdater(@Nonnull V newObject) { this.newObject = newObject; } @Nullable @Override public List<V> update(@Nonnull List<V> values) { if (values == ThreadSafeMultimap.NO_VALUE) { return null; } else if (!Iterables.contains(values, newObject)) { final List<V> result = ThreadSafeMultimap.copy(values); result.add(newObject); return result; } else { return null; } } }