ARROW-5973: [Java] Variable width vectors' get methods should return null when the underlying data is null

java/vector/src/main/java/org/apache/arrow/vector/FixedSizeBinaryVector.java

@@ -17,8 +17,6 @@
 
 package org.apache.arrow.vector;
 
-import static org.apache.arrow.vector.NullCheckingForGet.NULL_CHECKING_ENABLED;
-
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.vector.complex.impl.FixedSizeBinaryReaderImpl;
 import org.apache.arrow.vector.complex.reader.FieldReader;
@@ -115,8 +113,8 @@ public MinorType getMinorType() {
    */
   public byte[] get(int index) {
     assert index >= 0;
-    if (NULL_CHECKING_ENABLED && isSet(index) == 0) {
-      throw new IllegalStateException("Value at index is null");
+    if (isSet(index) == 0) {
+      return null;
     }
     final byte[] dst = new byte[byteWidth];
     valueBuffer.getBytes(index * byteWidth, dst, 0, byteWidth);
@@ -149,14 +147,7 @@ public void get(int index, NullableFixedSizeBinaryHolder holder) {
    */
   @Override
   public byte[] getObject(int index) {
-    assert index >= 0;
-    if (isSet(index) == 0) {
-      return null;
-    } else {
-      final byte[] dst = new byte[byteWidth];
-      valueBuffer.getBytes(index * byteWidth, dst, 0, byteWidth);
-      return dst;
-    }
+    return get(index);
   }
 
   public int getByteWidth() {

java/vector/src/main/java/org/apache/arrow/vector/VarBinaryVector.java

@@ -17,8 +17,6 @@
 
 package org.apache.arrow.vector;
 
-import static org.apache.arrow.vector.NullCheckingForGet.NULL_CHECKING_ENABLED;
-
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.vector.complex.impl.VarBinaryReaderImpl;
 import org.apache.arrow.vector.complex.reader.FieldReader;
@@ -110,8 +108,8 @@ public MinorType getMinorType() {
    */
   public byte[] get(int index) {
     assert index >= 0;
-    if (NULL_CHECKING_ENABLED && isSet(index) == 0) {
-      throw new IllegalStateException("Value at index is null");
+    if (isSet(index) == 0) {
+      return null;
     }
     final int startOffset = getStartOffset(index);
     final int dataLength =
@@ -128,13 +126,7 @@ public byte[] get(int index) {
    * @return byte array for non-null element, null otherwise
    */
   public byte[] getObject(int index) {
-    byte[] b;
-    try {
-      b = get(index);
-    } catch (IllegalStateException e) {
-      return null;
-    }
-    return b;
+    return get(index);
   }
 
   /**

java/vector/src/main/java/org/apache/arrow/vector/VarCharVector.java

@@ -17,8 +17,6 @@
 
 package org.apache.arrow.vector;
 
-import static org.apache.arrow.vector.NullCheckingForGet.NULL_CHECKING_ENABLED;
-
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.vector.complex.impl.VarCharReaderImpl;
 import org.apache.arrow.vector.complex.reader.FieldReader;
@@ -106,8 +104,8 @@ public MinorType getMinorType() {
    */
   public byte[] get(int index) {
     assert index >= 0;
-    if (NULL_CHECKING_ENABLED && isSet(index) == 0) {
-      throw new IllegalStateException("Value at index is null");
+    if (isSet(index) == 0) {
+      return null;
     }
     final int startOffset = getStartOffset(index);
     final int dataLength =
@@ -124,15 +122,12 @@ public byte[] get(int index) {
    * @return Text object for non-null element, null otherwise
    */
   public Text getObject(int index) {
-    Text result = new Text();
-    byte[] b;
-    try {
-      b = get(index);
-    } catch (IllegalStateException e) {
+    byte[] b = get(index);
+    if (b == null) {
       return null;
+    } else {
+      return new Text(b);
     }
-    result.set(b);
-    return result;
   }
 
   /**

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

@@ -258,4 +258,10 @@ public void setSetSafeWithInvalidInput() throws Exception {
     vector.setSafe(0, largeNullableHolder);
     vector.setSafe(0, largeBuf);
   }
+
+  @Test
+  public void testGetNull() {
+    vector.setNull(0);
+    assertNull(vector.get(0));
+  }
 }

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

@@ -906,13 +906,7 @@ public void testNullableVarType1() {
 
       // Ensure null value throws.
       boolean b = false;
-      try {
-        vector.get(8);
-      } catch (IllegalStateException e) {
-        b = true;
-      } finally {
-        assertTrue(b);
-      }
+      assertNull(vector.get(8));
     }
   }
 
@@ -942,14 +936,7 @@ public void testNullableVarType2() {
       assertArrayEquals(Arrays.copyOfRange(STR3, 2, STR3.length), vector.get(6));
 
       // Ensure null value throws.
-      boolean b = false;
-      try {
-        vector.get(7);
-      } catch (IllegalStateException e) {
-        b = true;
-      } finally {
-        assertTrue(b);
-      }
+      assertNull(vector.get(7));
     }
   }
 
@@ -2173,4 +2160,19 @@ public void testSetNullableVarBinaryHolderSafe() {
       buf.close();
     }
   }
+
+  @Test
+  public void testGetNullFromVariableWidthVector() {
+    try (VarCharVector varCharVector = new VarCharVector("varcharvec", allocator);
+    VarBinaryVector varBinaryVector = new VarBinaryVector("varbinary", allocator)) {
+      varCharVector.allocateNew(10, 1);
+      varBinaryVector.allocateNew(10, 1);
+
+      varCharVector.setNull(0);
+      varBinaryVector.setNull(0);
+
+      assertNull(varCharVector.get(0));
+      assertNull(varBinaryVector.get(0));
+    }
+  }
 }