| /* |
| * 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.flink.table.dataview; |
| |
| import java.util.Iterator; |
| import java.util.Map; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * An {@link Iterator} implementation that iterate on a map iterator and a null entry. |
| */ |
| public class NullAwareMapIterator<K, V> implements Iterator<Map.Entry<K, V>> { |
| |
| private final Iterator<Map.Entry<K, V>> mapIterator; |
| private final NullMapEntry<K, V> nullMapEntry; |
| private final boolean nullExisted; |
| private boolean nullVisited = false; |
| |
| public NullAwareMapIterator(Iterator<Map.Entry<K, V>> mapIterator, NullMapEntry<K, V> nullMapEntry) { |
| this.mapIterator = mapIterator; |
| this.nullMapEntry = nullMapEntry; |
| this.nullExisted = nullMapEntry.getValue() != null; |
| } |
| |
| @Override |
| public boolean hasNext() { |
| return mapIterator.hasNext() || (nullExisted && !nullVisited); |
| } |
| |
| @Override |
| public Map.Entry<K, V> next() { |
| if (mapIterator.hasNext()) { |
| return mapIterator.next(); |
| } else if (nullExisted && !nullVisited) { |
| this.nullVisited = true; |
| return nullMapEntry; |
| } else { |
| throw new NoSuchElementException(); |
| } |
| } |
| |
| @Override |
| public void remove() { |
| if (nullExisted && nullVisited) { |
| nullMapEntry.remove(); |
| } else { |
| mapIterator.remove(); |
| } |
| } |
| |
| /** |
| * A Map Entry that the entry key is always null. |
| */ |
| public interface NullMapEntry<K, V> extends Map.Entry<K, V> { |
| |
| @Override |
| default K getKey() { |
| // the key is always null |
| return null; |
| } |
| |
| void remove(); |
| } |
| } |