+/*
+ * (C) Copyright 2016 Pantheon Technologies, s.r.o. and others.
+ *
+ * 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.opendaylight.yangtools.triemap;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.AbstractSet;
+import java.util.Collection;
+
+/**
+ * Abstract base class for key set views of a TrieMap
+ *
+ * @author Robert Varga
+ *
+ * @param <K> the type of keys
+ */
+abstract class AbstractKeySet<K> extends AbstractSet<K> {
+ private final TrieMap<K, ?> map;
+
+ AbstractKeySet(final TrieMap<K, ?> map) {
+ this.map = checkNotNull(map);
+ }
+
+ final TrieMap<K, ?> map() {
+ return map;
+ }
+
+ @Override
+ public final boolean add(final K e) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public final boolean addAll(final Collection<? extends K> c) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public final boolean contains(final Object o) {
+ return map.containsKey(o);
+ }
+
+ @Override
+ public final boolean isEmpty() {
+ return map.isEmpty();
+ }
+
+ @Override
+ public final int size() {
+ return map.size();
+ }
+}