ARROW-4539: [Java] Fix child vector count for lists. (#3625)

* ARROW-4539: [Java] Fix child vector count for lists.

- Child vector count was not set correctly for lists. Fixed to use the right count.

* ARROW-4539: [Java] Add license header.

java/vector/src/main/java/org/apache/arrow/vector/complex/ListVector.java

@@ -744,7 +744,7 @@ public void setValueCount(int valueCount) {
  }
  /* valueCount for the data vector is the current end offset */
  final int childValueCount = (valueCount == 0) ? 0 :
- offsetBuffer.getInt(valueCount * OFFSET_WIDTH);
+ offsetBuffer.getInt(lastSet * OFFSET_WIDTH);
  /* set the value count of data vector and this will take care of
  * checking whether data buffer needs to be reallocated.
  */

java/vector/src/test/java/org/apache/arrow/vector/TestVarCharListVector.java

@@ -0,0 +1,78 @@
+/*
+ * 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.arrow.vector;
+
+import org.apache.arrow.memory.BufferAllocator;
+import org.apache.arrow.vector.complex.ListVector;
+import org.apache.arrow.vector.complex.impl.UnionListWriter;
+import org.apache.arrow.vector.types.Types;
+import org.apache.arrow.vector.types.pojo.FieldType;
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import io.netty.buffer.ArrowBuf;
+
+public class TestVarCharListVector {
+
+ private BufferAllocator allocator;
+
+ @Before
+ public void init() {
+ allocator = new DirtyRootAllocator(Long.MAX_VALUE, (byte) 100);
+ }
+
+ @After
+ public void terminate() throws Exception {
+ allocator.close();
+ }
+
+ @Test
+ public void testVarCharListWithNulls() {
+ byte[] bytes = "a".getBytes();
+ try (ListVector vector = new ListVector("VarList", allocator, FieldType.nullable(Types
+ .MinorType.VARCHAR.getType()),null);
+ ArrowBuf tempBuf = allocator.buffer(bytes.length)) {
+ UnionListWriter writer = vector.getWriter();
+ writer.allocate();
+
+ // populate input vector with the following records
+ // ["a"]
+ // null
+ // ["b"]
+ writer.setPosition(0); // optional
+ writer.startList();
+ tempBuf.setBytes(0, bytes);
+ writer.writeVarChar(0, bytes.length, tempBuf);
+ writer.endList();
+
+ writer.setPosition(2);
+ writer.startList();
+ bytes = "b".getBytes();
+ tempBuf.setBytes(0, bytes);
+ writer.writeVarChar(0, bytes.length, tempBuf);
+ writer.endList();
+
+ writer.setValueCount(2);
+
+ Assert.assertTrue(vector.getValueCount() == 2);
+ Assert.assertTrue(vector.getDataVector().getValueCount() == 2);
+ }
+ }
+}