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The following commit(s) were added to refs/heads/master by this push:
     new fe6f60c  ARROW-1885: [Java] Restore MapVector class names prior to 
ARROW-1710
fe6f60c is described below

commit fe6f60c31875c2a42d71a975f1c18c0c81c20678
Author: Bryan Cutler <cutl...@gmail.com>
AuthorDate: Mon Dec 4 17:46:12 2017 -0500

    ARROW-1885: [Java] Restore MapVector class names prior to ARROW-1710
    
    Changes to MapVector were not part of the intended goal for ARROW-1710 and 
should be restored to `NullableMapVector` -> `MapVector` -> `AbstractMapVector` 
as existed prior to #1341.
    
    Author: Bryan Cutler <cutl...@gmail.com>
    
    Closes #1389 from BryanCutler/java-restore-MapVector-class-ARROW-1885 and 
squashes the following commits:
    
    9ff503ab [Bryan Cutler] restore MapVector class names
    3d818f0e [Bryan Cutler] renamed NonNullableMapVector to MapVector
    ced1705c [Bryan Cutler] renamed MapVector to NullableMapVector
---
 .../codegen/templates/CaseSensitiveMapWriters.java |   2 +-
 .../src/main/codegen/templates/MapWriters.java     |   8 +-
 .../src/main/codegen/templates/UnionVector.java    |  10 +-
 .../arrow/vector/BaseVariableWidthVector.java      |   2 +-
 .../vector/complex/AbstractContainerVector.java    |   4 +-
 .../org/apache/arrow/vector/complex/MapVector.java | 552 ++++++++-------------
 .../arrow/vector/complex/NonNullableMapVector.java | 342 -------------
 .../{MapVector.java => NullableMapVector.java}     |  26 +-
 .../vector/complex/impl/ComplexWriterImpl.java     |   6 +-
 .../vector/complex/impl/NullableMapReaderImpl.java |   8 +-
 .../complex/impl/NullableMapWriterFactory.java     |   4 +-
 .../vector/complex/impl/PromotableWriter.java      |   4 +-
 .../vector/complex/impl/SingleMapReaderImpl.java   |   5 +-
 .../java/org/apache/arrow/vector/types/Types.java  |   6 +-
 .../org/apache/arrow/vector/TestMapVector.java     |   4 +-
 .../org/apache/arrow/vector/TestVectorReAlloc.java |   4 +-
 .../vector/complex/impl/TestPromotableWriter.java  |   4 +-
 .../vector/complex/writer/TestComplexWriter.java   |   6 +-
 .../org/apache/arrow/vector/ipc/BaseFileTest.java  |  12 +-
 .../org/apache/arrow/vector/ipc/TestArrowFile.java |  21 +-
 .../org/apache/arrow/vector/ipc/TestJSONFile.java  |  15 +-
 21 files changed, 271 insertions(+), 774 deletions(-)

diff --git 
a/java/vector/src/main/codegen/templates/CaseSensitiveMapWriters.java 
b/java/vector/src/main/codegen/templates/CaseSensitiveMapWriters.java
index 7c65290..5357f9b 100644
--- a/java/vector/src/main/codegen/templates/CaseSensitiveMapWriters.java
+++ b/java/vector/src/main/codegen/templates/CaseSensitiveMapWriters.java
@@ -23,7 +23,7 @@
 <#if mode == "Single">
 <#assign containerClass = "MapVector" />
 <#else>
-<#assign containerClass = "MapVector" />
+<#assign containerClass = "NullableMapVector" />
 </#if>
 
 <#include "/@includes/license.ftl" />
diff --git a/java/vector/src/main/codegen/templates/MapWriters.java 
b/java/vector/src/main/codegen/templates/MapWriters.java
index a5ac1b7..ac59e59 100644
--- a/java/vector/src/main/codegen/templates/MapWriters.java
+++ b/java/vector/src/main/codegen/templates/MapWriters.java
@@ -21,9 +21,9 @@
 <@pp.changeOutputFile 
name="/org/apache/arrow/vector/complex/impl/${mode}MapWriter.java" />
 <#assign index = "idx()">
 <#if mode == "Single">
-<#assign containerClass = "NonNullableMapVector" />
-<#else>
 <#assign containerClass = "MapVector" />
+<#else>
+<#assign containerClass = "NullableMapVector" />
 </#if>
 
 <#include "/@includes/license.ftl" />
@@ -51,7 +51,7 @@ public class ${mode}MapWriter extends AbstractFieldWriter {
   private final Map<String, FieldWriter> fields = Maps.newHashMap();
   public ${mode}MapWriter(${containerClass} container) {
     <#if mode == "Single">
-    if (container instanceof MapVector) {
+    if (container instanceof NullableMapVector) {
       throw new IllegalArgumentException("Invalid container: " + container);
     }
     </#if>
@@ -124,7 +124,7 @@ public class ${mode}MapWriter extends AbstractFieldWriter {
     FieldWriter writer = fields.get(finalName);
     if(writer == null){
       int vectorCount=container.size();
-      MapVector vector = container.addOrGet(name, 
FieldType.nullable(MinorType.MAP.getType()), MapVector.class);
+      NullableMapVector vector = container.addOrGet(name, 
FieldType.nullable(MinorType.MAP.getType()), NullableMapVector.class);
       writer = new PromotableWriter(vector, container, 
getNullableMapWriterFactory());
       if(vectorCount != container.size()) {
         writer.allocate();
diff --git a/java/vector/src/main/codegen/templates/UnionVector.java 
b/java/vector/src/main/codegen/templates/UnionVector.java
index 60cd24d..9377bd0 100644
--- a/java/vector/src/main/codegen/templates/UnionVector.java
+++ b/java/vector/src/main/codegen/templates/UnionVector.java
@@ -48,8 +48,8 @@ import static org.apache.arrow.vector.types.UnionMode.Sparse;
 
 
 /**
- * A vector which can hold values of different types. It does so by using a 
MapVector which contains a vector for each
- * primitive type that is stored. MapVector is used in order to take advantage 
of its serialization/deserialization methods,
+ * A vector which can hold values of different types. It does so by using a 
NullableMapVector which contains a vector for each
+ * primitive type that is stored. NullableMapVector is used in order to take 
advantage of its serialization/deserialization methods,
  * as well as the addOrGet method.
  *
  * For performance reasons, UnionVector stores a cached reference to each 
subtype vector, to avoid having to do the map lookup
@@ -65,7 +65,7 @@ public class UnionVector implements FieldVector {
   MapVector internalMap;
   protected ArrowBuf typeBuffer;
 
-  private MapVector mapVector;
+  private NullableMapVector mapVector;
   private ListVector listVector;
 
   private FieldReader reader;
@@ -174,10 +174,10 @@ public class UnionVector implements FieldVector {
   @Override
   public ArrowBuf getOffsetBuffer() { throw new 
UnsupportedOperationException(); }
 
-  public MapVector getMap() {
+  public NullableMapVector getMap() {
     if (mapVector == null) {
       int vectorCount = internalMap.size();
-      mapVector = addOrGet(MinorType.MAP, MapVector.class);
+      mapVector = addOrGet(MinorType.MAP, NullableMapVector.class);
       if (internalMap.size() > vectorCount) {
         mapVector.allocateNew();
         if (callBack != null) {
diff --git 
a/java/vector/src/main/java/org/apache/arrow/vector/BaseVariableWidthVector.java
 
b/java/vector/src/main/java/org/apache/arrow/vector/BaseVariableWidthVector.java
index 98820a2..fbadb35 100644
--- 
a/java/vector/src/main/java/org/apache/arrow/vector/BaseVariableWidthVector.java
+++ 
b/java/vector/src/main/java/org/apache/arrow/vector/BaseVariableWidthVector.java
@@ -24,7 +24,7 @@ import io.netty.buffer.ArrowBuf;
 import org.apache.arrow.memory.OutOfMemoryException;
 import org.apache.arrow.memory.BaseAllocator;
 import org.apache.arrow.memory.BufferAllocator;
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import org.apache.arrow.vector.ipc.message.ArrowFieldNode;
 import org.apache.arrow.vector.types.pojo.Field;
 import org.apache.arrow.vector.types.pojo.FieldType;
diff --git 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/AbstractContainerVector.java
 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/AbstractContainerVector.java
index 5ded1cc..db0ff86 100644
--- 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/AbstractContainerVector.java
+++ 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/AbstractContainerVector.java
@@ -100,8 +100,8 @@ public abstract class AbstractContainerVector implements 
ValueVector {
   // return the child vector's ordinal in the composite container
   public abstract VectorWithOrdinal getChildVectorWithOrdinal(String name);
 
-  public MapVector addOrGetMap(String name) {
-    return addOrGet(name, FieldType.nullable(new Struct()), MapVector.class);
+  public NullableMapVector addOrGetMap(String name) {
+    return addOrGet(name, FieldType.nullable(new Struct()), 
NullableMapVector.class);
   }
 
   public ListVector addOrGetList(String name) {
diff --git 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/MapVector.java 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/MapVector.java
index 72cc29f..e130845 100644
--- a/java/vector/src/main/java/org/apache/arrow/vector/complex/MapVector.java
+++ b/java/vector/src/main/java/org/apache/arrow/vector/complex/MapVector.java
@@ -6,9 +6,9 @@
  * 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
- * <p>
+ *
  * http://www.apache.org/licenses/LICENSE-2.0
- * <p>
+ *
  * 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.
@@ -21,480 +21,322 @@ package org.apache.arrow.vector.complex;
 import static com.google.common.base.Preconditions.checkNotNull;
 
 import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collections;
+import java.util.Collection;
+import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
 
-import com.google.common.collect.ObjectArrays;
+import javax.annotation.Nullable;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.Ordering;
+import com.google.common.primitives.Ints;
 
 import io.netty.buffer.ArrowBuf;
-import org.apache.arrow.memory.BaseAllocator;
+
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.vector.*;
-import org.apache.arrow.vector.complex.impl.NullableMapReaderImpl;
-import org.apache.arrow.vector.complex.impl.NullableMapWriter;
+import org.apache.arrow.vector.complex.impl.SingleMapReaderImpl;
+import org.apache.arrow.vector.complex.reader.FieldReader;
 import org.apache.arrow.vector.holders.ComplexHolder;
-import org.apache.arrow.vector.ipc.message.ArrowFieldNode;
+import org.apache.arrow.vector.types.Types.MinorType;
 import org.apache.arrow.vector.types.pojo.ArrowType;
-import org.apache.arrow.vector.types.pojo.ArrowType.Struct;
-import org.apache.arrow.vector.types.pojo.DictionaryEncoding;
-import org.apache.arrow.vector.types.pojo.FieldType;
 import org.apache.arrow.vector.types.pojo.Field;
+import org.apache.arrow.vector.types.pojo.FieldType;
 import org.apache.arrow.vector.util.CallBack;
-import org.apache.arrow.vector.util.OversizedAllocationException;
+import org.apache.arrow.vector.util.JsonStringHashMap;
 import org.apache.arrow.vector.util.TransferPair;
 
-public class MapVector extends NonNullableMapVector implements FieldVector {
+public class MapVector extends AbstractMapVector {
+  //private static final org.slf4j.Logger logger = 
org.slf4j.LoggerFactory.getLogger(MapVector.class);
 
   public static MapVector empty(String name, BufferAllocator allocator) {
-    FieldType fieldType = FieldType.nullable(Struct.INSTANCE);
+    FieldType fieldType = new FieldType(false, ArrowType.Struct.INSTANCE, 
null, null);
     return new MapVector(name, allocator, fieldType, null);
   }
 
-  private final NullableMapReaderImpl reader = new NullableMapReaderImpl(this);
-  private final NullableMapWriter writer = new NullableMapWriter(this);
-
-  protected ArrowBuf validityBuffer;
-  private int validityAllocationSizeInBytes;
+  private final SingleMapReaderImpl reader = new SingleMapReaderImpl(this);
+  protected final FieldType fieldType;
+  public int valueCount;
 
   // deprecated, use FieldType or static constructor instead
   @Deprecated
   public MapVector(String name, BufferAllocator allocator, CallBack callBack) {
-    this(name, allocator, FieldType.nullable(ArrowType.Struct.INSTANCE), 
callBack);
+    this(name, allocator, new FieldType(false, ArrowType.Struct.INSTANCE, 
null, null), callBack);
   }
 
-  // deprecated, use FieldType or static constructor instead
-  @Deprecated
-  public MapVector(String name, BufferAllocator allocator, DictionaryEncoding 
dictionary, CallBack callBack) {
-    this(name, allocator, new FieldType(true, ArrowType.Struct.INSTANCE, 
dictionary, null), callBack);
+  public MapVector(String name, BufferAllocator allocator, FieldType 
fieldType, CallBack callBack) {
+    super(name, allocator, callBack);
+    this.fieldType = checkNotNull(fieldType);
+    this.valueCount = 0;
   }
 
-  public MapVector(String name, BufferAllocator allocator, FieldType 
fieldType, CallBack callBack) {
-    super(name, checkNotNull(allocator), fieldType, callBack);
-    this.validityBuffer = allocator.getEmpty();
-    this.validityAllocationSizeInBytes = 
BitVectorHelper.getValidityBufferSize(BaseValueVector.INITIAL_VALUE_ALLOCATION);
+  @Override
+  public FieldReader getReader() {
+    return reader;
+  }
+
+  transient private MapTransferPair ephPair;
+
+  public void copyFromSafe(int fromIndex, int thisIndex, MapVector from) {
+    if (ephPair == null || ephPair.from != from) {
+      ephPair = (MapTransferPair) from.makeTransferPair(this);
+    }
+    ephPair.copyValueSafe(fromIndex, thisIndex);
   }
 
   @Override
-  public Field getField() {
-    Field f = super.getField();
-    FieldType type = new FieldType(true, f.getType(), 
f.getFieldType().getDictionary(), f.getFieldType().getMetadata());
-    return new Field(f.getName(), type, f.getChildren());
+  protected boolean supportsDirectRead() {
+    return true;
+  }
+
+  public Iterator<String> fieldNameIterator() {
+    return getChildFieldNames().iterator();
   }
 
   @Override
-  public void loadFieldBuffers(ArrowFieldNode fieldNode, List<ArrowBuf> 
ownBuffers) {
-    if (ownBuffers.size() != 1) {
-      throw new IllegalArgumentException("Illegal buffer count, expected " + 1 
+ ", got: " + ownBuffers.size());
+  public void setInitialCapacity(int numRecords) {
+    for (final ValueVector v : (Iterable<ValueVector>) this) {
+      v.setInitialCapacity(numRecords);
     }
+  }
 
-    ArrowBuf bitBuffer = ownBuffers.get(0);
+  @Override
+  public int getBufferSize() {
+    if (valueCount == 0 || size() == 0) {
+      return 0;
+    }
+    long buffer = 0;
+    for (final ValueVector v : (Iterable<ValueVector>) this) {
+      buffer += v.getBufferSize();
+    }
 
-    validityBuffer.release();
-    validityBuffer = BitVectorHelper.loadValidityBuffer(fieldNode, bitBuffer, 
allocator);
-    valueCount = fieldNode.getLength();
-    validityAllocationSizeInBytes = validityBuffer.capacity();
+    return (int) buffer;
   }
 
   @Override
-  public List<ArrowBuf> getFieldBuffers() {
-    List<ArrowBuf> result = new ArrayList<>(1);
-    setReaderAndWriterIndex();
-    result.add(validityBuffer);
+  public int getBufferSizeFor(final int valueCount) {
+    if (valueCount == 0) {
+      return 0;
+    }
 
-    return result;
-  }
+    long bufferSize = 0;
+    for (final ValueVector v : (Iterable<ValueVector>) this) {
+      bufferSize += v.getBufferSizeFor(valueCount);
+    }
 
-  private void setReaderAndWriterIndex() {
-    validityBuffer.readerIndex(0);
-    
validityBuffer.writerIndex(BitVectorHelper.getValidityBufferSize(valueCount));
+    return (int) bufferSize;
   }
 
   @Override
-  @Deprecated
-  public List<BufferBacked> getFieldInnerVectors() {
-    throw new UnsupportedOperationException("There are no inner vectors. Use 
getFieldBuffers");
+  public ArrowBuf getValidityBuffer() {
+    throw new UnsupportedOperationException();
   }
 
   @Override
-  public NullableMapReaderImpl getReader() {
-    return reader;
+  public ArrowBuf getDataBuffer() {
+    throw new UnsupportedOperationException();
   }
 
-  public NullableMapWriter getWriter() {
-    return writer;
+  @Override
+  public ArrowBuf getOffsetBuffer() {
+    throw new UnsupportedOperationException();
   }
 
   @Override
   public TransferPair getTransferPair(BufferAllocator allocator) {
-    return new NullableMapTransferPair(this, new MapVector(name, allocator, 
fieldType, null), false);
+    return getTransferPair(name, allocator, null);
   }
 
   @Override
-  public TransferPair makeTransferPair(ValueVector to) {
-    return new NullableMapTransferPair(this, (MapVector) to, true);
+  public TransferPair getTransferPair(String ref, BufferAllocator allocator, 
CallBack callBack) {
+    return new MapTransferPair(this, new MapVector(name, allocator, fieldType, 
callBack), false);
   }
 
   @Override
-  public TransferPair getTransferPair(String ref, BufferAllocator allocator) {
-    return new NullableMapTransferPair(this, new MapVector(ref, allocator, 
fieldType, null), false);
+  public TransferPair makeTransferPair(ValueVector to) {
+    return new MapTransferPair(this, (MapVector) to);
   }
 
   @Override
-  public TransferPair getTransferPair(String ref, BufferAllocator allocator, 
CallBack callBack) {
-    return new NullableMapTransferPair(this, new MapVector(ref, allocator, 
fieldType, callBack), false);
+  public TransferPair getTransferPair(String ref, BufferAllocator allocator) {
+    return new MapTransferPair(this, new MapVector(ref, allocator, fieldType, 
callBack), false);
   }
 
-  protected class NullableMapTransferPair extends MapTransferPair {
-
-    private MapVector target;
+  protected static class MapTransferPair implements TransferPair {
+    private final TransferPair[] pairs;
+    private final MapVector from;
+    private final MapVector to;
 
-    protected NullableMapTransferPair(MapVector from, MapVector to, boolean 
allocate) {
-      super(from, to, allocate);
-      this.target = to;
+    public MapTransferPair(MapVector from, MapVector to) {
+      this(from, to, true);
     }
 
-    @Override
-    public void transfer() {
-      target.clear();
-      target.validityBuffer = 
validityBuffer.transferOwnership(target.allocator).buffer;
-      super.transfer();
-      clear();
+    protected MapTransferPair(MapVector from, MapVector to, boolean allocate) {
+      this.from = from;
+      this.to = to;
+      this.pairs = new TransferPair[from.size()];
+      this.to.ephPair = null;
+
+      int i = 0;
+      FieldVector vector;
+      for (String child : from.getChildFieldNames()) {
+        int preSize = to.size();
+        vector = from.getChild(child);
+        if (vector == null) {
+          continue;
+        }
+        //DRILL-1872: we add the child fields for the vector, looking up the 
field by name. For a map vector,
+        // the child fields may be nested fields of the top level child. For 
example if the structure
+        // of a child field is oa.oab.oabc then we add oa, then add oab to oa 
then oabc to oab.
+        // But the children member of a Materialized field is a HashSet. If 
the fields are added in the
+        // children HashSet, and the hashCode of the Materialized field 
includes the hash code of the
+        // children, the hashCode value of oa changes *after* the field has 
been added to the HashSet.
+        // (This is similar to what happens in ScanBatch where the children 
cannot be added till they are
+        // read). To take care of this, we ensure that the hashCode of the 
MaterializedField does not
+        // include the hashCode of the children but is based only on 
MaterializedField$key.
+        final FieldVector newVector = to.addOrGet(child, 
vector.getField().getFieldType(), vector.getClass());
+        if (allocate && to.size() != preSize) {
+          newVector.allocateNew();
+        }
+        pairs[i++] = vector.makeTransferPair(newVector);
+      }
     }
 
     @Override
-    public void copyValueSafe(int fromIndex, int toIndex) {
-      while (toIndex >= target.getValidityBufferValueCapacity()) {
-        target.reallocValidityBuffer();
+    public void transfer() {
+      for (final TransferPair p : pairs) {
+        p.transfer();
       }
-      BitVectorHelper.setValidityBit(target.validityBuffer, toIndex, 
isSet(fromIndex));
-      super.copyValueSafe(fromIndex, toIndex);
+      to.valueCount = from.valueCount;
+      from.clear();
     }
 
     @Override
-    public void splitAndTransfer(int startIndex, int length) {
-      target.clear();
-      splitAndTransferValidityBuffer(startIndex, length, target);
-      super.splitAndTransfer(startIndex, length);
+    public ValueVector getTo() {
+      return to;
     }
-  }
 
-  /*
-   * transfer the validity.
-   */
-  private void splitAndTransferValidityBuffer(int startIndex, int length, 
MapVector target) {
-    assert startIndex + length <= valueCount;
-    int firstByteSource = BitVectorHelper.byteIndex(startIndex);
-    int lastByteSource = BitVectorHelper.byteIndex(valueCount - 1);
-    int byteSizeTarget = BitVectorHelper.getValidityBufferSize(length);
-    int offset = startIndex % 8;
-
-    if (length > 0) {
-      if (offset == 0) {
-        // slice
-        if (target.validityBuffer != null) {
-          target.validityBuffer.release();
-        }
-        target.validityBuffer = validityBuffer.slice(firstByteSource, 
byteSizeTarget);
-        target.validityBuffer.retain(1);
-      } else {
-        /* Copy data
-         * When the first bit starts from the middle of a byte (offset != 0),
-         * copy data from src BitVector.
-         * Each byte in the target is composed by a part in i-th byte,
-         * another part in (i+1)-th byte.
-         */
-        target.allocateValidityBuffer(byteSizeTarget);
-
-        for (int i = 0; i < byteSizeTarget - 1; i++) {
-          byte b1 = BitVectorHelper.getBitsFromCurrentByte(validityBuffer, 
firstByteSource + i, offset);
-          byte b2 = BitVectorHelper.getBitsFromNextByte(validityBuffer, 
firstByteSource + i + 1, offset);
-
-          target.validityBuffer.setByte(i, (b1 + b2));
-        }
-
-        /* Copying the last piece is done in the following manner:
-         * if the source vector has 1 or more bytes remaining, we copy
-         * the last piece as a byte formed by shifting data
-         * from the current byte and the next byte.
-         *
-         * if the source vector has no more bytes remaining
-         * (we are at the last byte), we copy the last piece as a byte
-         * by shifting data from the current byte.
-         */
-        if ((firstByteSource + byteSizeTarget - 1) < lastByteSource) {
-          byte b1 = BitVectorHelper.getBitsFromCurrentByte(validityBuffer,
-                  firstByteSource + byteSizeTarget - 1, offset);
-          byte b2 = BitVectorHelper.getBitsFromNextByte(validityBuffer,
-                  firstByteSource + byteSizeTarget, offset);
-
-          target.validityBuffer.setByte(byteSizeTarget - 1, b1 + b2);
-        } else {
-          byte b1 = BitVectorHelper.getBitsFromCurrentByte(validityBuffer,
-                  firstByteSource + byteSizeTarget - 1, offset);
-          target.validityBuffer.setByte(byteSizeTarget - 1, b1);
-        }
+    @Override
+    public void copyValueSafe(int from, int to) {
+      for (TransferPair p : pairs) {
+        p.copyValueSafe(from, to);
       }
     }
-  }
-
-  /**
-   * Get the value capacity of the internal validity buffer.
-   * @return number of elements that validity buffer can hold
-   */
-  private int getValidityBufferValueCapacity() {
-    return (int) (validityBuffer.capacity() * 8L);
-  }
-
-  /**
-   * Get the current value capacity for the vector
-   * @return number of elements that vector can hold.
-   */
-  @Override
-  public int getValueCapacity() {
-    return Math.min(getValidityBufferValueCapacity(),
-            super.getValueCapacity());
-  }
 
-  /**
-   * Return the underlying buffers associated with this vector. Note that this 
doesn't
-   * impact the reference counts for this buffer so it only should be used for 
in-context
-   * access. Also note that this buffer changes regularly thus
-   * external classes shouldn't hold a reference to it (unless they change it).
-   *
-   * @param clear Whether to clear vector before returning; the buffers will 
still be refcounted
-   *              but the returned array will be the only reference to them
-   * @return The underlying {@link io.netty.buffer.ArrowBuf buffers} that is 
used by this
-   *         vector instance.
-   */
-  @Override
-  public ArrowBuf[] getBuffers(boolean clear) {
-    setReaderAndWriterIndex();
-    final ArrowBuf[] buffers;
-    if (getBufferSize() == 0) {
-      buffers = new ArrowBuf[0];
-    } else {
-      buffers = ObjectArrays.concat(new ArrowBuf[]{validityBuffer}, 
super.getBuffers(false),
-              ArrowBuf.class);
-    }
-    if (clear) {
-      for (ArrowBuf buffer : buffers) {
-        buffer.retain();
+    @Override
+    public void splitAndTransfer(int startIndex, int length) {
+      for (TransferPair p : pairs) {
+        p.splitAndTransfer(startIndex, length);
       }
-      clear();
+      to.setValueCount(length);
     }
-
-    return buffers;
   }
 
-  /**
-   * Close the vector and release the associated buffers.
-   */
   @Override
-  public void close() {
-    clearValidityBuffer();
-    super.close();
-  }
-
-  /**
-   * Same as {@link #close()}
-   */
-  @Override
-  public void clear() {
-    clearValidityBuffer();
-    super.clear();
-  }
-
-  /**
-   * Release the validity buffer
-   */
-  private void clearValidityBuffer() {
-    validityBuffer.release();
-    validityBuffer = allocator.getEmpty();
-  }
-
-  /**
-   * Get the size (number of bytes) of underlying buffers used by this
-   * vector
-   * @return size of underlying buffers.
-   */
-  @Override
-  public int getBufferSize() {
-    if (valueCount == 0) {
+  public int getValueCapacity() {
+    if (size() == 0) {
       return 0;
     }
-    return super.getBufferSize() +
-            BitVectorHelper.getValidityBufferSize(valueCount);
-  }
 
-  /**
-   * Get the potential buffer size for a particular number of records.
-   * @param valueCount desired number of elements in the vector
-   * @return estimated size of underlying buffers if the vector holds
-   *         a given number of elements
-   */
-  @Override
-  public int getBufferSizeFor(final int valueCount) {
-    if (valueCount == 0) {
-      return 0;
-    }
-    return super.getBufferSizeFor(valueCount)
-            + BitVectorHelper.getValidityBufferSize(valueCount);
-  }
+    final Ordering<ValueVector> natural = new Ordering<ValueVector>() {
+      @Override
+      public int compare(@Nullable ValueVector left, @Nullable ValueVector 
right) {
+        return Ints.compare(
+            checkNotNull(left).getValueCapacity(),
+            checkNotNull(right).getValueCapacity()
+        );
+      }
+    };
 
-  @Override
-  public void setInitialCapacity(int numRecords) {
-    validityAllocationSizeInBytes = 
BitVectorHelper.getValidityBufferSize(numRecords);
-    super.setInitialCapacity(numRecords);
+    return natural.min(getChildren()).getValueCapacity();
   }
 
   @Override
-  public boolean allocateNewSafe() {
-    /* Boolean to keep track if all the memory allocations were successful
-     * Used in the case of composite vectors when we need to allocate multiple
-     * buffers for multiple vectors. If one of the allocations failed we need 
to
-     * clear all the memory that we allocated
-     */
-    boolean success = false;
-    try {
-      clear();
-      allocateValidityBuffer(validityAllocationSizeInBytes);
-      success = super.allocateNewSafe();
-    } finally {
-      if (!success) {
-        clear();
-        return false;
+  public Object getObject(int index) {
+    Map<String, Object> vv = new JsonStringHashMap<>();
+    for (String child : getChildFieldNames()) {
+      ValueVector v = getChild(child);
+      if (v != null && index < v.getValueCount()) {
+        Object value = v.getObject(index);
+        if (value != null) {
+          vv.put(child, value);
+        }
       }
     }
-    return true;
-  }
-
-  private void allocateValidityBuffer(final long size) {
-    final int curSize = (int) size;
-    validityBuffer = allocator.buffer(curSize);
-    validityBuffer.readerIndex(0);
-    validityAllocationSizeInBytes = curSize;
-    validityBuffer.setZero(0, validityBuffer.capacity());
+    return vv;
   }
 
   @Override
-  public void reAlloc() {
-    /* reallocate the validity buffer */
-    reallocValidityBuffer();
-    super.reAlloc();
-  }
-
-  private void reallocValidityBuffer() {
-    final int currentBufferCapacity = validityBuffer.capacity();
-    long baseSize = validityAllocationSizeInBytes;
-
-    if (baseSize < (long) currentBufferCapacity) {
-      baseSize = (long) currentBufferCapacity;
-    }
-
-    long newAllocationSize = baseSize * 2L;
-    newAllocationSize = BaseAllocator.nextPowerOfTwo(newAllocationSize);
-
-    if (newAllocationSize > BaseValueVector.MAX_ALLOCATION_SIZE) {
-      throw new OversizedAllocationException("Unable to expand the buffer");
-    }
-
-    final ArrowBuf newBuf = allocator.buffer((int) newAllocationSize);
-    newBuf.setZero(0, newBuf.capacity());
-    newBuf.setBytes(0, validityBuffer, 0, currentBufferCapacity);
-    validityBuffer.release(1);
-    validityBuffer = newBuf;
-    validityAllocationSizeInBytes = (int) newAllocationSize;
-  }
-
+  public boolean isNull(int index) { return false; }
   @Override
-  public long getValidityBufferAddress() {
-    return validityBuffer.memoryAddress();
-  }
+  public int getNullCount() { return 0; }
 
-  @Override
-  public long getDataBufferAddress() {
-    throw new UnsupportedOperationException();
+  public void get(int index, ComplexHolder holder) {
+    reader.setPosition(index);
+    holder.reader = reader;
   }
 
   @Override
-  public long getOffsetBufferAddress() {
-    throw new UnsupportedOperationException();
+  public int getValueCount() {
+    return valueCount;
   }
 
-  @Override
-  public ArrowBuf getValidityBuffer() {
-    return validityBuffer;
-  }
+  public ValueVector getVectorById(int id) {
+  return getChildByOrdinal(id);
+}
 
   @Override
-  public ArrowBuf getDataBuffer() {
-    throw new UnsupportedOperationException();
+  public void setValueCount(int valueCount) {
+    for (final ValueVector v : getChildren()) {
+      v.setValueCount(valueCount);
+    }
+    MapVector.this.valueCount = valueCount;
   }
 
   @Override
-  public ArrowBuf getOffsetBuffer() {
-    throw new UnsupportedOperationException();
+  public void clear() {
+    for (final ValueVector v : getChildren()) {
+      v.clear();
+    }
+    valueCount = 0;
   }
 
   @Override
-  public Object getObject(int index) {
-    if (isSet(index) == 0) {
-      return null;
-    } else {
-      return super.getObject(index);
+  public Field getField() {
+    List<Field> children = new ArrayList<>();
+    for (ValueVector child : getChildren()) {
+      children.add(child.getField());
     }
+    return new Field(name, fieldType, children);
   }
 
   @Override
-  public void get(int index, ComplexHolder holder) {
-    holder.isSet = isSet(index);
-    super.get(index, holder);
+  public MinorType getMinorType() {
+    return MinorType.MAP;
   }
 
-  public int getNullCount() {
-    return BitVectorHelper.getNullCount(validityBuffer, valueCount);
-  }
-
-  public boolean isNull(int index) {
-    return isSet(index) == 0;
-  }
-
-  public int isSet(int index) {
-    final int byteIndex = index >> 3;
-    final byte b = validityBuffer.getByte(byteIndex);
-    final int bitIndex = index & 7;
-    return Long.bitCount(b & (1L << bitIndex));
-  }
-
-  public void setIndexDefined(int index) {
-    while (index >= getValidityBufferValueCapacity()) {
-      /* realloc the inner buffers if needed */
-      reallocValidityBuffer();
+  @Override
+  public void close() {
+    final Collection<FieldVector> vectors = getChildren();
+    for (final FieldVector v : vectors) {
+      v.close();
     }
-    BitVectorHelper.setValidityBitToOne(validityBuffer, index);
-  }
+    vectors.clear();
 
-  public void setNull(int index) {
-    while (index >= getValidityBufferValueCapacity()) {
-      /* realloc the inner buffers if needed */
-      reallocValidityBuffer();
-    }
-    BitVectorHelper.setValidityBit(validityBuffer, index, 0);
+    valueCount = 0;
+
+    super.close();
   }
 
-  @Override
-  public void setValueCount(int valueCount) {
-    assert valueCount >= 0;
-    while (valueCount > getValidityBufferValueCapacity()) {
-      /* realloc the inner buffers if needed */
-      reallocValidityBuffer();
+  public void initializeChildrenFromFields(List<Field> children) {
+    for (Field field : children) {
+      FieldVector vector = (FieldVector) this.add(field.getName(), 
field.getFieldType());
+      vector.initializeChildrenFromFields(field.getChildren());
     }
-    super.setValueCount(valueCount);
-    this.valueCount = valueCount;
   }
 
-  public void reset() {
-    valueCount = 0;
+  public List<FieldVector> getChildrenFromFields() {
+    return getChildren();
   }
 }
diff --git 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/NonNullableMapVector.java
 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/NonNullableMapVector.java
deleted file mode 100644
index 1cd7b70..0000000
--- 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/NonNullableMapVector.java
+++ /dev/null
@@ -1,342 +0,0 @@
-/**
- * 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.complex;
-
-import static com.google.common.base.Preconditions.checkNotNull;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
-
-import javax.annotation.Nullable;
-
-import com.google.common.base.Preconditions;
-import com.google.common.collect.Ordering;
-import com.google.common.primitives.Ints;
-
-import io.netty.buffer.ArrowBuf;
-
-import org.apache.arrow.memory.BufferAllocator;
-import org.apache.arrow.vector.*;
-import org.apache.arrow.vector.complex.impl.SingleMapReaderImpl;
-import org.apache.arrow.vector.complex.reader.FieldReader;
-import org.apache.arrow.vector.holders.ComplexHolder;
-import org.apache.arrow.vector.types.Types.MinorType;
-import org.apache.arrow.vector.types.pojo.ArrowType;
-import org.apache.arrow.vector.types.pojo.Field;
-import org.apache.arrow.vector.types.pojo.FieldType;
-import org.apache.arrow.vector.util.CallBack;
-import org.apache.arrow.vector.util.JsonStringHashMap;
-import org.apache.arrow.vector.util.TransferPair;
-
-public class NonNullableMapVector extends AbstractMapVector {
-  //private static final org.slf4j.Logger logger = 
org.slf4j.LoggerFactory.getLogger(NonNullableMapVector.class);
-
-  public static NonNullableMapVector empty(String name, BufferAllocator 
allocator) {
-    FieldType fieldType = new FieldType(false, ArrowType.Struct.INSTANCE, 
null, null);
-    return new NonNullableMapVector(name, allocator, fieldType, null);
-  }
-
-  private final SingleMapReaderImpl reader = new SingleMapReaderImpl(this);
-  protected final FieldType fieldType;
-  public int valueCount;
-
-  // deprecated, use FieldType or static constructor instead
-  @Deprecated
-  public NonNullableMapVector(String name, BufferAllocator allocator, CallBack 
callBack) {
-    this(name, allocator, new FieldType(false, ArrowType.Struct.INSTANCE, 
null, null), callBack);
-  }
-
-  public NonNullableMapVector(String name, BufferAllocator allocator, 
FieldType fieldType, CallBack callBack) {
-    super(name, allocator, callBack);
-    this.fieldType = checkNotNull(fieldType);
-    this.valueCount = 0;
-  }
-
-  @Override
-  public FieldReader getReader() {
-    return reader;
-  }
-
-  transient private MapTransferPair ephPair;
-
-  public void copyFromSafe(int fromIndex, int thisIndex, NonNullableMapVector 
from) {
-    if (ephPair == null || ephPair.from != from) {
-      ephPair = (MapTransferPair) from.makeTransferPair(this);
-    }
-    ephPair.copyValueSafe(fromIndex, thisIndex);
-  }
-
-  @Override
-  protected boolean supportsDirectRead() {
-    return true;
-  }
-
-  public Iterator<String> fieldNameIterator() {
-    return getChildFieldNames().iterator();
-  }
-
-  @Override
-  public void setInitialCapacity(int numRecords) {
-    for (final ValueVector v : (Iterable<ValueVector>) this) {
-      v.setInitialCapacity(numRecords);
-    }
-  }
-
-  @Override
-  public int getBufferSize() {
-    if (valueCount == 0 || size() == 0) {
-      return 0;
-    }
-    long buffer = 0;
-    for (final ValueVector v : (Iterable<ValueVector>) this) {
-      buffer += v.getBufferSize();
-    }
-
-    return (int) buffer;
-  }
-
-  @Override
-  public int getBufferSizeFor(final int valueCount) {
-    if (valueCount == 0) {
-      return 0;
-    }
-
-    long bufferSize = 0;
-    for (final ValueVector v : (Iterable<ValueVector>) this) {
-      bufferSize += v.getBufferSizeFor(valueCount);
-    }
-
-    return (int) bufferSize;
-  }
-
-  @Override
-  public ArrowBuf getValidityBuffer() {
-    throw new UnsupportedOperationException();
-  }
-
-  @Override
-  public ArrowBuf getDataBuffer() {
-    throw new UnsupportedOperationException();
-  }
-
-  @Override
-  public ArrowBuf getOffsetBuffer() {
-    throw new UnsupportedOperationException();
-  }
-
-  @Override
-  public TransferPair getTransferPair(BufferAllocator allocator) {
-    return getTransferPair(name, allocator, null);
-  }
-
-  @Override
-  public TransferPair getTransferPair(String ref, BufferAllocator allocator, 
CallBack callBack) {
-    return new MapTransferPair(this, new NonNullableMapVector(name, allocator, 
fieldType, callBack), false);
-  }
-
-  @Override
-  public TransferPair makeTransferPair(ValueVector to) {
-    return new MapTransferPair(this, (NonNullableMapVector) to);
-  }
-
-  @Override
-  public TransferPair getTransferPair(String ref, BufferAllocator allocator) {
-    return new MapTransferPair(this, new NonNullableMapVector(ref, allocator, 
fieldType, callBack), false);
-  }
-
-  protected static class MapTransferPair implements TransferPair {
-    private final TransferPair[] pairs;
-    private final NonNullableMapVector from;
-    private final NonNullableMapVector to;
-
-    public MapTransferPair(NonNullableMapVector from, NonNullableMapVector to) 
{
-      this(from, to, true);
-    }
-
-    protected MapTransferPair(NonNullableMapVector from, NonNullableMapVector 
to, boolean allocate) {
-      this.from = from;
-      this.to = to;
-      this.pairs = new TransferPair[from.size()];
-      this.to.ephPair = null;
-
-      int i = 0;
-      FieldVector vector;
-      for (String child : from.getChildFieldNames()) {
-        int preSize = to.size();
-        vector = from.getChild(child);
-        if (vector == null) {
-          continue;
-        }
-        //DRILL-1872: we add the child fields for the vector, looking up the 
field by name. For a map vector,
-        // the child fields may be nested fields of the top level child. For 
example if the structure
-        // of a child field is oa.oab.oabc then we add oa, then add oab to oa 
then oabc to oab.
-        // But the children member of a Materialized field is a HashSet. If 
the fields are added in the
-        // children HashSet, and the hashCode of the Materialized field 
includes the hash code of the
-        // children, the hashCode value of oa changes *after* the field has 
been added to the HashSet.
-        // (This is similar to what happens in ScanBatch where the children 
cannot be added till they are
-        // read). To take care of this, we ensure that the hashCode of the 
MaterializedField does not
-        // include the hashCode of the children but is based only on 
MaterializedField$key.
-        final FieldVector newVector = to.addOrGet(child, 
vector.getField().getFieldType(), vector.getClass());
-        if (allocate && to.size() != preSize) {
-          newVector.allocateNew();
-        }
-        pairs[i++] = vector.makeTransferPair(newVector);
-      }
-    }
-
-    @Override
-    public void transfer() {
-      for (final TransferPair p : pairs) {
-        p.transfer();
-      }
-      to.valueCount = from.valueCount;
-      from.clear();
-    }
-
-    @Override
-    public ValueVector getTo() {
-      return to;
-    }
-
-    @Override
-    public void copyValueSafe(int from, int to) {
-      for (TransferPair p : pairs) {
-        p.copyValueSafe(from, to);
-      }
-    }
-
-    @Override
-    public void splitAndTransfer(int startIndex, int length) {
-      for (TransferPair p : pairs) {
-        p.splitAndTransfer(startIndex, length);
-      }
-      to.setValueCount(length);
-    }
-  }
-
-  @Override
-  public int getValueCapacity() {
-    if (size() == 0) {
-      return 0;
-    }
-
-    final Ordering<ValueVector> natural = new Ordering<ValueVector>() {
-      @Override
-      public int compare(@Nullable ValueVector left, @Nullable ValueVector 
right) {
-        return Ints.compare(
-            checkNotNull(left).getValueCapacity(),
-            checkNotNull(right).getValueCapacity()
-        );
-      }
-    };
-
-    return natural.min(getChildren()).getValueCapacity();
-  }
-
-  @Override
-  public Object getObject(int index) {
-    Map<String, Object> vv = new JsonStringHashMap<>();
-    for (String child : getChildFieldNames()) {
-      ValueVector v = getChild(child);
-      if (v != null && index < v.getValueCount()) {
-        Object value = v.getObject(index);
-        if (value != null) {
-          vv.put(child, value);
-        }
-      }
-    }
-    return vv;
-  }
-
-  @Override
-  public boolean isNull(int index) { return false; }
-  @Override
-  public int getNullCount() { return 0; }
-
-  public void get(int index, ComplexHolder holder) {
-    reader.setPosition(index);
-    holder.reader = reader;
-  }
-
-  @Override
-  public int getValueCount() {
-    return valueCount;
-  }
-
-  public ValueVector getVectorById(int id) {
-  return getChildByOrdinal(id);
-}
-
-  @Override
-  public void setValueCount(int valueCount) {
-    for (final ValueVector v : getChildren()) {
-      v.setValueCount(valueCount);
-    }
-    NonNullableMapVector.this.valueCount = valueCount;
-  }
-
-  @Override
-  public void clear() {
-    for (final ValueVector v : getChildren()) {
-      v.clear();
-    }
-    valueCount = 0;
-  }
-
-  @Override
-  public Field getField() {
-    List<Field> children = new ArrayList<>();
-    for (ValueVector child : getChildren()) {
-      children.add(child.getField());
-    }
-    return new Field(name, fieldType, children);
-  }
-
-  @Override
-  public MinorType getMinorType() {
-    return MinorType.MAP;
-  }
-
-  @Override
-  public void close() {
-    final Collection<FieldVector> vectors = getChildren();
-    for (final FieldVector v : vectors) {
-      v.close();
-    }
-    vectors.clear();
-
-    valueCount = 0;
-
-    super.close();
-  }
-
-  public void initializeChildrenFromFields(List<Field> children) {
-    for (Field field : children) {
-      FieldVector vector = (FieldVector) this.add(field.getName(), 
field.getFieldType());
-      vector.initializeChildrenFromFields(field.getChildren());
-    }
-  }
-
-  public List<FieldVector> getChildrenFromFields() {
-    return getChildren();
-  }
-}
diff --git 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/MapVector.java 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/NullableMapVector.java
similarity index 93%
copy from 
java/vector/src/main/java/org/apache/arrow/vector/complex/MapVector.java
copy to 
java/vector/src/main/java/org/apache/arrow/vector/complex/NullableMapVector.java
index 72cc29f..d887b73 100644
--- a/java/vector/src/main/java/org/apache/arrow/vector/complex/MapVector.java
+++ 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/NullableMapVector.java
@@ -44,11 +44,11 @@ import org.apache.arrow.vector.util.CallBack;
 import org.apache.arrow.vector.util.OversizedAllocationException;
 import org.apache.arrow.vector.util.TransferPair;
 
-public class MapVector extends NonNullableMapVector implements FieldVector {
+public class NullableMapVector extends MapVector implements FieldVector {
 
-  public static MapVector empty(String name, BufferAllocator allocator) {
+  public static NullableMapVector empty(String name, BufferAllocator 
allocator) {
     FieldType fieldType = FieldType.nullable(Struct.INSTANCE);
-    return new MapVector(name, allocator, fieldType, null);
+    return new NullableMapVector(name, allocator, fieldType, null);
   }
 
   private final NullableMapReaderImpl reader = new NullableMapReaderImpl(this);
@@ -59,17 +59,17 @@ public class MapVector extends NonNullableMapVector 
implements FieldVector {
 
   // deprecated, use FieldType or static constructor instead
   @Deprecated
-  public MapVector(String name, BufferAllocator allocator, CallBack callBack) {
+  public NullableMapVector(String name, BufferAllocator allocator, CallBack 
callBack) {
     this(name, allocator, FieldType.nullable(ArrowType.Struct.INSTANCE), 
callBack);
   }
 
   // deprecated, use FieldType or static constructor instead
   @Deprecated
-  public MapVector(String name, BufferAllocator allocator, DictionaryEncoding 
dictionary, CallBack callBack) {
+  public NullableMapVector(String name, BufferAllocator allocator, 
DictionaryEncoding dictionary, CallBack callBack) {
     this(name, allocator, new FieldType(true, ArrowType.Struct.INSTANCE, 
dictionary, null), callBack);
   }
 
-  public MapVector(String name, BufferAllocator allocator, FieldType 
fieldType, CallBack callBack) {
+  public NullableMapVector(String name, BufferAllocator allocator, FieldType 
fieldType, CallBack callBack) {
     super(name, checkNotNull(allocator), fieldType, callBack);
     this.validityBuffer = allocator.getEmpty();
     this.validityAllocationSizeInBytes = 
BitVectorHelper.getValidityBufferSize(BaseValueVector.INITIAL_VALUE_ALLOCATION);
@@ -127,29 +127,29 @@ public class MapVector extends NonNullableMapVector 
implements FieldVector {
 
   @Override
   public TransferPair getTransferPair(BufferAllocator allocator) {
-    return new NullableMapTransferPair(this, new MapVector(name, allocator, 
fieldType, null), false);
+    return new NullableMapTransferPair(this, new NullableMapVector(name, 
allocator, fieldType, null), false);
   }
 
   @Override
   public TransferPair makeTransferPair(ValueVector to) {
-    return new NullableMapTransferPair(this, (MapVector) to, true);
+    return new NullableMapTransferPair(this, (NullableMapVector) to, true);
   }
 
   @Override
   public TransferPair getTransferPair(String ref, BufferAllocator allocator) {
-    return new NullableMapTransferPair(this, new MapVector(ref, allocator, 
fieldType, null), false);
+    return new NullableMapTransferPair(this, new NullableMapVector(ref, 
allocator, fieldType, null), false);
   }
 
   @Override
   public TransferPair getTransferPair(String ref, BufferAllocator allocator, 
CallBack callBack) {
-    return new NullableMapTransferPair(this, new MapVector(ref, allocator, 
fieldType, callBack), false);
+    return new NullableMapTransferPair(this, new NullableMapVector(ref, 
allocator, fieldType, callBack), false);
   }
 
   protected class NullableMapTransferPair extends MapTransferPair {
 
-    private MapVector target;
+    private NullableMapVector target;
 
-    protected NullableMapTransferPair(MapVector from, MapVector to, boolean 
allocate) {
+    protected NullableMapTransferPair(NullableMapVector from, 
NullableMapVector to, boolean allocate) {
       super(from, to, allocate);
       this.target = to;
     }
@@ -182,7 +182,7 @@ public class MapVector extends NonNullableMapVector 
implements FieldVector {
   /*
    * transfer the validity.
    */
-  private void splitAndTransferValidityBuffer(int startIndex, int length, 
MapVector target) {
+  private void splitAndTransferValidityBuffer(int startIndex, int length, 
NullableMapVector target) {
     assert startIndex + length <= valueCount;
     int firstByteSource = BitVectorHelper.byteIndex(startIndex);
     int lastByteSource = BitVectorHelper.byteIndex(valueCount - 1);
diff --git 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/ComplexWriterImpl.java
 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/ComplexWriterImpl.java
index 970b90e..a696023 100644
--- 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/ComplexWriterImpl.java
+++ 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/ComplexWriterImpl.java
@@ -20,7 +20,7 @@ package org.apache.arrow.vector.complex.impl;
 
 import org.apache.arrow.vector.complex.ListVector;
 import org.apache.arrow.vector.complex.MapVector;
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import org.apache.arrow.vector.complex.StateTool;
 import org.apache.arrow.vector.complex.writer.BaseWriter.ComplexWriter;
 import org.apache.arrow.vector.types.pojo.Field;
@@ -131,7 +131,7 @@ public class ComplexWriterImpl extends AbstractFieldWriter 
implements ComplexWri
     switch (mode) {
 
       case INIT:
-        mapRoot = nullableMapWriterFactory.build((MapVector) container);
+        mapRoot = nullableMapWriterFactory.build((NullableMapVector) 
container);
         mapRoot.setPosition(idx());
         mode = Mode.MAP;
         break;
@@ -152,7 +152,7 @@ public class ComplexWriterImpl extends AbstractFieldWriter 
implements ComplexWri
 
       case INIT:
         // TODO allow dictionaries in complex types
-        MapVector map = container.addOrGetMap(name);
+        NullableMapVector map = container.addOrGetMap(name);
         mapRoot = nullableMapWriterFactory.build(map);
         mapRoot.setPosition(idx());
         mode = Mode.MAP;
diff --git 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/NullableMapReaderImpl.java
 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/NullableMapReaderImpl.java
index acf155a..06b0f4d 100644
--- 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/NullableMapReaderImpl.java
+++ 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/NullableMapReaderImpl.java
@@ -20,17 +20,17 @@
 package org.apache.arrow.vector.complex.impl;
 
 import org.apache.arrow.vector.complex.MapVector;
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import org.apache.arrow.vector.complex.writer.BaseWriter.MapWriter;
 import org.apache.arrow.vector.types.pojo.Field;
 
 public class NullableMapReaderImpl extends SingleMapReaderImpl {
 
-  private MapVector nullableMapVector;
+  private NullableMapVector nullableMapVector;
 
   public NullableMapReaderImpl(MapVector vector) {
-    super((MapVector) vector);
-    this.nullableMapVector = (MapVector) vector;
+    super((NullableMapVector) vector);
+    this.nullableMapVector = (NullableMapVector) vector;
   }
 
   @Override
diff --git 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/NullableMapWriterFactory.java
 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/NullableMapWriterFactory.java
index 06dbf78..d2dcb23 100644
--- 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/NullableMapWriterFactory.java
+++ 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/NullableMapWriterFactory.java
@@ -18,7 +18,7 @@
 
 package org.apache.arrow.vector.complex.impl;
 
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 
 public class NullableMapWriterFactory {
   private final boolean caseSensitive;
@@ -29,7 +29,7 @@ public class NullableMapWriterFactory {
     this.caseSensitive = caseSensitive;
   }
 
-  public NullableMapWriter build(MapVector container) {
+  public NullableMapWriter build(NullableMapVector container) {
     return this.caseSensitive ? new NullableCaseSensitiveMapWriter(container) 
: new NullableMapWriter(container);
   }
 
diff --git 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/PromotableWriter.java
 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/PromotableWriter.java
index 9abd38d..5bd439c 100644
--- 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/PromotableWriter.java
+++ 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/PromotableWriter.java
@@ -23,7 +23,7 @@ import org.apache.arrow.vector.ValueVector;
 import org.apache.arrow.vector.ZeroVector;
 import org.apache.arrow.vector.complex.AbstractMapVector;
 import org.apache.arrow.vector.complex.ListVector;
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import org.apache.arrow.vector.complex.UnionVector;
 import org.apache.arrow.vector.complex.writer.FieldWriter;
 import org.apache.arrow.vector.types.Types.MinorType;
@@ -94,7 +94,7 @@ public class PromotableWriter extends 
AbstractPromotableFieldWriter {
     type = v.getMinorType();
     switch (type) {
       case MAP:
-        writer = nullableMapWriterFactory.build((MapVector) vector);
+        writer = nullableMapWriterFactory.build((NullableMapVector) vector);
         break;
       case LIST:
         writer = new UnionListWriter((ListVector) vector, 
nullableMapWriterFactory);
diff --git 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/SingleMapReaderImpl.java
 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/SingleMapReaderImpl.java
index 0341b62..c77ca4e 100644
--- 
a/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/SingleMapReaderImpl.java
+++ 
b/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/SingleMapReaderImpl.java
@@ -24,7 +24,6 @@ import java.util.Map;
 
 import org.apache.arrow.vector.ValueVector;
 import org.apache.arrow.vector.complex.MapVector;
-import org.apache.arrow.vector.complex.NonNullableMapVector;
 import org.apache.arrow.vector.complex.reader.FieldReader;
 import org.apache.arrow.vector.complex.writer.BaseWriter.MapWriter;
 import org.apache.arrow.vector.types.Types.MinorType;
@@ -35,10 +34,10 @@ import com.google.common.collect.Maps;
 @SuppressWarnings("unused")
 public class SingleMapReaderImpl extends AbstractFieldReader {
 
-  private final NonNullableMapVector vector;
+  private final MapVector vector;
   private final Map<String, FieldReader> fields = Maps.newHashMap();
 
-  public SingleMapReaderImpl(NonNullableMapVector vector) {
+  public SingleMapReaderImpl(MapVector vector) {
     this.vector = vector;
   }
 
diff --git a/java/vector/src/main/java/org/apache/arrow/vector/types/Types.java 
b/java/vector/src/main/java/org/apache/arrow/vector/types/Types.java
index 7834845..3c5fd81 100644
--- a/java/vector/src/main/java/org/apache/arrow/vector/types/Types.java
+++ b/java/vector/src/main/java/org/apache/arrow/vector/types/Types.java
@@ -58,7 +58,7 @@ import org.apache.arrow.vector.ValueVector;
 import org.apache.arrow.vector.ZeroVector;
 import org.apache.arrow.vector.complex.FixedSizeListVector;
 import org.apache.arrow.vector.complex.ListVector;
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import org.apache.arrow.vector.complex.UnionVector;
 import org.apache.arrow.vector.complex.impl.BigIntWriterImpl;
 import org.apache.arrow.vector.complex.impl.BitWriterImpl;
@@ -131,12 +131,12 @@ public class Types {
     MAP(Struct.INSTANCE) {
       @Override
       public FieldVector getNewVector(String name, FieldType fieldType, 
BufferAllocator allocator, CallBack schemaChangeCallback) {
-        return new MapVector(name, allocator, fieldType, schemaChangeCallback);
+        return new NullableMapVector(name, allocator, fieldType, 
schemaChangeCallback);
       }
 
       @Override
       public FieldWriter getNewFieldWriter(ValueVector vector) {
-        return new NullableMapWriter((MapVector) vector);
+        return new NullableMapWriter((NullableMapVector) vector);
       }
     },
     TINYINT(new Int(8, true)) {
diff --git 
a/java/vector/src/test/java/org/apache/arrow/vector/TestMapVector.java 
b/java/vector/src/test/java/org/apache/arrow/vector/TestMapVector.java
index e568295..357df96 100644
--- a/java/vector/src/test/java/org/apache/arrow/vector/TestMapVector.java
+++ b/java/vector/src/test/java/org/apache/arrow/vector/TestMapVector.java
@@ -22,7 +22,7 @@ import java.util.HashMap;
 import java.util.Map;
 
 import org.apache.arrow.memory.BufferAllocator;
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import org.apache.arrow.vector.types.pojo.ArrowType.Struct;
 import org.apache.arrow.vector.types.pojo.FieldType;
 import org.junit.After;
@@ -50,7 +50,7 @@ public class TestMapVector {
     Map<String, String> metadata = new HashMap<>();
     metadata.put("k1", "v1");
     FieldType type = new FieldType(true, Struct.INSTANCE, null, metadata);
-    try (MapVector vector = new MapVector("map", allocator, type, null)) {
+    try (NullableMapVector vector = new NullableMapVector("map", allocator, 
type, null)) {
       Assert.assertEquals(vector.getField().getMetadata(), type.getMetadata());
     }
   }
diff --git 
a/java/vector/src/test/java/org/apache/arrow/vector/TestVectorReAlloc.java 
b/java/vector/src/test/java/org/apache/arrow/vector/TestVectorReAlloc.java
index 1b13c2e..f8edf89 100644
--- a/java/vector/src/test/java/org/apache/arrow/vector/TestVectorReAlloc.java
+++ b/java/vector/src/test/java/org/apache/arrow/vector/TestVectorReAlloc.java
@@ -26,7 +26,7 @@ import java.nio.charset.StandardCharsets;
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.memory.RootAllocator;
 import org.apache.arrow.vector.complex.ListVector;
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import org.apache.arrow.vector.types.Types.MinorType;
 import org.apache.arrow.vector.types.pojo.ArrowType;
 import org.apache.arrow.vector.types.pojo.FieldType;
@@ -121,7 +121,7 @@ public class TestVectorReAlloc {
 
   @Test
   public void testMapType() {
-    try (final MapVector vector = MapVector.empty("", allocator)) {
+    try (final NullableMapVector vector = NullableMapVector.empty("", 
allocator)) {
       vector.addOrGet("", FieldType.nullable(MinorType.INT.getType()), 
IntVector.class);
 
       vector.setInitialCapacity(512);
diff --git 
a/java/vector/src/test/java/org/apache/arrow/vector/complex/impl/TestPromotableWriter.java
 
b/java/vector/src/test/java/org/apache/arrow/vector/complex/impl/TestPromotableWriter.java
index 38b7842..b0d6cf5 100644
--- 
a/java/vector/src/test/java/org/apache/arrow/vector/complex/impl/TestPromotableWriter.java
+++ 
b/java/vector/src/test/java/org/apache/arrow/vector/complex/impl/TestPromotableWriter.java
@@ -25,7 +25,7 @@ import static org.junit.Assert.assertTrue;
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.vector.DirtyRootAllocator;
 import org.apache.arrow.vector.complex.MapVector;
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import org.apache.arrow.vector.complex.UnionVector;
 import org.apache.arrow.vector.complex.writer.BaseWriter.MapWriter;
 import org.apache.arrow.vector.types.pojo.ArrowType;
@@ -55,7 +55,7 @@ public class TestPromotableWriter {
   public void testPromoteToUnion() throws Exception {
 
     try (final MapVector container = MapVector.empty(EMPTY_SCHEMA_PATH, 
allocator);
-         final MapVector v = container.addOrGetMap("test");
+         final NullableMapVector v = container.addOrGetMap("test");
          final PromotableWriter writer = new PromotableWriter(v, container)) {
 
       container.allocateNew();
diff --git 
a/java/vector/src/test/java/org/apache/arrow/vector/complex/writer/TestComplexWriter.java
 
b/java/vector/src/test/java/org/apache/arrow/vector/complex/writer/TestComplexWriter.java
index bd8489e..29d39aa 100644
--- 
a/java/vector/src/test/java/org/apache/arrow/vector/complex/writer/TestComplexWriter.java
+++ 
b/java/vector/src/test/java/org/apache/arrow/vector/complex/writer/TestComplexWriter.java
@@ -34,7 +34,7 @@ import org.apache.arrow.vector.BigIntVector;
 import org.apache.arrow.vector.IntVector;
 import org.apache.arrow.vector.complex.ListVector;
 import org.apache.arrow.vector.complex.MapVector;
-import org.apache.arrow.vector.complex.NonNullableMapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import org.apache.arrow.vector.complex.UnionVector;
 import org.apache.arrow.vector.complex.impl.ComplexWriterImpl;
 import org.apache.arrow.vector.complex.impl.SingleMapReaderImpl;
@@ -830,7 +830,7 @@ public class TestComplexWriter {
     rootWriter.end();
     writer.setValueCount(1);
 
-    MapVector mapVector = (MapVector) parent.getChild("root");
+    NullableMapVector mapVector = (NullableMapVector) parent.getChild("root");
     TransferPair tp = mapVector.getTransferPair(allocator);
     tp.splitAndTransfer(0, 1);
     MapVector toMapVector = (MapVector) tp.getTo();
@@ -849,7 +849,7 @@ public class TestComplexWriter {
     /* initialize a SingleMapWriter with empty MapVector and then lazily
      * create all vectors with expected initialCapacity.
      */
-    NonNullableMapVector parent = NonNullableMapVector.empty("parent", 
allocator);
+    MapVector parent = MapVector.empty("parent", allocator);
     SingleMapWriter singleMapWriter = new SingleMapWriter(parent);
 
     int initialCapacity = 1024;
diff --git 
a/java/vector/src/test/java/org/apache/arrow/vector/ipc/BaseFileTest.java 
b/java/vector/src/test/java/org/apache/arrow/vector/ipc/BaseFileTest.java
index 1a7f71c..9eb55c9 100644
--- a/java/vector/src/test/java/org/apache/arrow/vector/ipc/BaseFileTest.java
+++ b/java/vector/src/test/java/org/apache/arrow/vector/ipc/BaseFileTest.java
@@ -36,7 +36,7 @@ import org.apache.arrow.vector.VarBinaryVector;
 import org.apache.arrow.vector.VarCharVector;
 import org.apache.arrow.vector.VectorSchemaRoot;
 import org.apache.arrow.vector.complex.ListVector;
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import org.apache.arrow.vector.complex.impl.ComplexWriterImpl;
 import org.apache.arrow.vector.complex.impl.UnionListWriter;
 import org.apache.arrow.vector.complex.reader.FieldReader;
@@ -94,7 +94,7 @@ public class BaseFileTest {
     DateTimeZone.setDefault(defaultTimezone);
   }
 
-  protected void writeData(int count, MapVector parent) {
+  protected void writeData(int count, NullableMapVector parent) {
     ComplexWriter writer = new ComplexWriterImpl("root", parent);
     MapWriter rootWriter = writer.rootAsMap();
     IntWriter intWriter = rootWriter.integer("int");
@@ -119,7 +119,7 @@ public class BaseFileTest {
     }
   }
 
-  protected void writeComplexData(int count, MapVector parent) {
+  protected void writeComplexData(int count, NullableMapVector parent) {
     ArrowBuf varchar = allocator.buffer(3);
     varchar.readerIndex(0);
     varchar.setByte(0, 'a');
@@ -189,7 +189,7 @@ public class BaseFileTest {
     return new LocalDateTime(2000 + i, 1 + i, 1 + i, i, i, i, i);
   }
 
-  protected void writeDateTimeData(int count, MapVector parent) {
+  protected void writeDateTimeData(int count, NullableMapVector parent) {
     Assert.assertTrue(count < 100);
     ComplexWriter writer = new ComplexWriterImpl("root", parent);
     MapWriter rootWriter = writer.rootAsMap();
@@ -494,7 +494,7 @@ public class BaseFileTest {
     }
   }
 
-  public void writeUnionData(int count, MapVector parent) {
+  public void writeUnionData(int count, NullableMapVector parent) {
     ArrowBuf varchar = allocator.buffer(3);
     varchar.readerIndex(0);
     varchar.setByte(0, 'a');
@@ -537,7 +537,7 @@ public class BaseFileTest {
     varchar.release();
   }
 
-  protected void writeVarBinaryData(int count, MapVector parent) {
+  protected void writeVarBinaryData(int count, NullableMapVector parent) {
     Assert.assertTrue(count < 100);
     ComplexWriter writer = new ComplexWriterImpl("root", parent);
     MapWriter rootWriter = writer.rootAsMap();
diff --git 
a/java/vector/src/test/java/org/apache/arrow/vector/ipc/TestArrowFile.java 
b/java/vector/src/test/java/org/apache/arrow/vector/ipc/TestArrowFile.java
index 0cfc9ba..055c34e 100644
--- a/java/vector/src/test/java/org/apache/arrow/vector/ipc/TestArrowFile.java
+++ b/java/vector/src/test/java/org/apache/arrow/vector/ipc/TestArrowFile.java
@@ -42,8 +42,7 @@ import org.apache.arrow.vector.TinyIntVector;
 import org.apache.arrow.vector.VectorSchemaRoot;
 import org.apache.arrow.vector.VectorUnloader;
 import org.apache.arrow.vector.complex.FixedSizeListVector;
-import org.apache.arrow.vector.complex.MapVector;
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import 
org.apache.arrow.vector.dictionary.DictionaryProvider.MapDictionaryProvider;
 import org.apache.arrow.vector.ipc.message.ArrowBlock;
 import org.apache.arrow.vector.ipc.message.ArrowBuffer;
@@ -70,7 +69,7 @@ public class TestArrowFile extends BaseFileTest {
     int count = COUNT;
     try (
         BufferAllocator vectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-        MapVector parent = MapVector.empty("parent", vectorAllocator)) {
+        NullableMapVector parent = NullableMapVector.empty("parent", 
vectorAllocator)) {
       writeData(count, parent);
       write(parent.getChild("root"), file, new ByteArrayOutputStream());
     }
@@ -82,7 +81,7 @@ public class TestArrowFile extends BaseFileTest {
     int count = COUNT;
     try (
         BufferAllocator vectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-        MapVector parent = MapVector.empty("parent", vectorAllocator)) {
+        NullableMapVector parent = NullableMapVector.empty("parent", 
vectorAllocator)) {
       writeComplexData(count, parent);
       FieldVector root = parent.getChild("root");
       validateComplexContent(count, new VectorSchemaRoot(root));
@@ -98,7 +97,7 @@ public class TestArrowFile extends BaseFileTest {
 
     // write
     try (BufferAllocator originalVectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-         MapVector parent = MapVector.empty("parent", 
originalVectorAllocator)) {
+         NullableMapVector parent = NullableMapVector.empty("parent", 
originalVectorAllocator)) {
       writeData(count, parent);
       write(parent.getChild("root"), file, stream);
     }
@@ -154,7 +153,7 @@ public class TestArrowFile extends BaseFileTest {
 
     // write
     try (BufferAllocator originalVectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-         MapVector parent = MapVector.empty("parent", 
originalVectorAllocator)) {
+         NullableMapVector parent = NullableMapVector.empty("parent", 
originalVectorAllocator)) {
       writeComplexData(count, parent);
       write(parent.getChild("root"), file, stream);
     }
@@ -195,7 +194,7 @@ public class TestArrowFile extends BaseFileTest {
 
     // write
     try (BufferAllocator originalVectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-         MapVector parent = MapVector.empty("parent", originalVectorAllocator);
+         NullableMapVector parent = NullableMapVector.empty("parent", 
originalVectorAllocator);
          FileOutputStream fileOutputStream = new FileOutputStream(file)) {
       writeData(counts[0], parent);
       VectorSchemaRoot root = new VectorSchemaRoot(parent.getChild("root"));
@@ -268,7 +267,7 @@ public class TestArrowFile extends BaseFileTest {
 
     // write
     try (BufferAllocator vectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-         MapVector parent = MapVector.empty("parent", vectorAllocator)) {
+         NullableMapVector parent = NullableMapVector.empty("parent", 
vectorAllocator)) {
       writeUnionData(count, parent);
       validateUnionData(count, new VectorSchemaRoot(parent.getChild("root")));
       write(parent.getChild("root"), file, stream);
@@ -382,7 +381,7 @@ public class TestArrowFile extends BaseFileTest {
 
     // write
     try (BufferAllocator originalVectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-         MapVector vector = (MapVector) 
field.createVector(originalVectorAllocator)) {
+         NullableMapVector vector = (NullableMapVector) 
field.createVector(originalVectorAllocator)) {
       vector.allocateNewSafe();
       vector.setValueCount(0);
 
@@ -558,7 +557,7 @@ public class TestArrowFile extends BaseFileTest {
 
     // write
     try (BufferAllocator originalVectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-         MapVector parent = MapVector.empty("parent", 
originalVectorAllocator)) {
+         NullableMapVector parent = NullableMapVector.empty("parent", 
originalVectorAllocator)) {
       FixedSizeListVector tuples = parent.addOrGet("float-pairs", 
FieldType.nullable(new FixedSizeList(2)), FixedSizeListVector.class);
       Float4Vector floats = (Float4Vector) 
tuples.addOrGetVector(FieldType.nullable(MinorType.FLOAT4.getType())).getVector();
       IntVector ints = parent.addOrGet("ints", FieldType.nullable(new Int(32, 
true)), IntVector.class);
@@ -618,7 +617,7 @@ public class TestArrowFile extends BaseFileTest {
     // write
     try (
         BufferAllocator vectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-        MapVector parent = MapVector.empty("parent", vectorAllocator)) {
+        NullableMapVector parent = NullableMapVector.empty("parent", 
vectorAllocator)) {
       writeVarBinaryData(count, parent);
       VectorSchemaRoot root = new VectorSchemaRoot(parent.getChild("root"));
       validateVarBinary(count, root);
diff --git 
a/java/vector/src/test/java/org/apache/arrow/vector/ipc/TestJSONFile.java 
b/java/vector/src/test/java/org/apache/arrow/vector/ipc/TestJSONFile.java
index 4f9093b..6a23a84 100644
--- a/java/vector/src/test/java/org/apache/arrow/vector/ipc/TestJSONFile.java
+++ b/java/vector/src/test/java/org/apache/arrow/vector/ipc/TestJSONFile.java
@@ -24,8 +24,7 @@ import java.io.IOException;
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.vector.FieldVector;
 import org.apache.arrow.vector.VectorSchemaRoot;
-import org.apache.arrow.vector.complex.MapVector;
-import org.apache.arrow.vector.complex.MapVector;
+import org.apache.arrow.vector.complex.NullableMapVector;
 import org.apache.arrow.vector.dictionary.DictionaryProvider;
 import 
org.apache.arrow.vector.dictionary.DictionaryProvider.MapDictionaryProvider;
 import org.apache.arrow.vector.types.pojo.Schema;
@@ -45,7 +44,7 @@ public class TestJSONFile extends BaseFileTest {
 
     // write
     try (BufferAllocator originalVectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-         MapVector parent = MapVector.empty("parent", 
originalVectorAllocator)) {
+         NullableMapVector parent = NullableMapVector.empty("parent", 
originalVectorAllocator)) {
       writeData(count, parent);
       writeJSON(file, new VectorSchemaRoot(parent.getChild("root")), null);
     }
@@ -73,7 +72,7 @@ public class TestJSONFile extends BaseFileTest {
     // write
     try (
         BufferAllocator originalVectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-        MapVector parent = MapVector.empty("parent", originalVectorAllocator)) 
{
+        NullableMapVector parent = NullableMapVector.empty("parent", 
originalVectorAllocator)) {
       writeComplexData(count, parent);
       writeJSON(file, new VectorSchemaRoot(parent.getChild("root")), null);
     }
@@ -100,7 +99,7 @@ public class TestJSONFile extends BaseFileTest {
     int count = COUNT;
     try (
         BufferAllocator vectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-        MapVector parent = MapVector.empty("parent", vectorAllocator)) {
+        NullableMapVector parent = NullableMapVector.empty("parent", 
vectorAllocator)) {
       writeComplexData(count, parent);
       VectorSchemaRoot root = new VectorSchemaRoot(parent.getChild("root"));
       validateComplexContent(root.getRowCount(), root);
@@ -122,7 +121,7 @@ public class TestJSONFile extends BaseFileTest {
     int count = COUNT;
     try (
         BufferAllocator vectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-        MapVector parent = MapVector.empty("parent", vectorAllocator)) {
+        NullableMapVector parent = NullableMapVector.empty("parent", 
vectorAllocator)) {
       writeUnionData(count, parent);
       printVectors(parent.getChildrenFromFields());
 
@@ -154,7 +153,7 @@ public class TestJSONFile extends BaseFileTest {
     // write
     try (
         BufferAllocator vectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-        MapVector parent = MapVector.empty("parent", vectorAllocator)) {
+        NullableMapVector parent = NullableMapVector.empty("parent", 
vectorAllocator)) {
 
       writeDateTimeData(count, parent);
 
@@ -319,7 +318,7 @@ public class TestJSONFile extends BaseFileTest {
     // write
     try (
         BufferAllocator vectorAllocator = 
allocator.newChildAllocator("original vectors", 0, Integer.MAX_VALUE);
-        MapVector parent = MapVector.empty("parent", vectorAllocator)) {
+        NullableMapVector parent = NullableMapVector.empty("parent", 
vectorAllocator)) {
       writeVarBinaryData(count, parent);
       VectorSchemaRoot root = new VectorSchemaRoot(parent.getChild("root"));
       validateVarBinary(count, root);

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