Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/4585#discussion_r141097303
--- Diff:
flink-core/src/main/java/org/apache/flink/api/java/typeutils/MultisetTypeInfo.java
---
@@ -0,0 +1,133 @@
+/*
+ * 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.api.java.typeutils;
+
+import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.api.common.typeinfo.BasicTypeInfo;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+
+import java.util.Map;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+
+/**
+ * A {@link TypeInformation} for the Multiset types of the Java API.
+ *
+ * @param <T> The type of the elements in the Multiset.
+ */
+@PublicEvolving
+public final class MultisetTypeInfo<T> extends MapTypeInfo<T, Integer> {
+
+ private static final long serialVersionUID = 1L;
+
+
+ public MultisetTypeInfo(Class<T> elementTypeClass) {
+ super(elementTypeClass, Integer.class);
+ }
+
+ public MultisetTypeInfo(TypeInformation<T> elementTypeInfo) {
+ super(elementTypeInfo, BasicTypeInfo.INT_TYPE_INFO);
+ }
+
+ //
------------------------------------------------------------------------
+ // MultisetTypeInfo specific properties
+ //
------------------------------------------------------------------------
+
+ /**
+ * Gets the type information for the elements contained in the Multiset
+ */
+ public TypeInformation<T> getElementTypeInfo() {
+ return getKeyTypeInfo();
+ }
+
+ //
------------------------------------------------------------------------
+ // TypeInformation implementation
+ //
------------------------------------------------------------------------
+
+ @Override
+ public boolean isBasicType() {
+ return false;
+ }
+
+ @Override
+ public boolean isTupleType() {
+ return false;
+ }
+
+ @Override
+ public int getArity() {
+ return 0;
+ }
+
+ @Override
+ public int getTotalFields() {
+ // similar as arrays, the multiset are "opaque" to the direct
field addressing logic
+ // since the multiset's elements are not addressable, we do not
expose them
+ return 1;
+ }
+
+ @SuppressWarnings("unchecked")
+ @Override
+ public Class<Map<T, Integer>> getTypeClass() {
+ return (Class<Map<T, Integer>>)(Class<?>)Map.class;
+ }
+
+ @Override
+ public boolean isKeyType() {
--- End diff --
implemented by `MapTypeInfo`, no need to override.
---
