GH-1302: Follow vector transfer implementation style

Change-Id: If49bdef2c665414b786ea0f2b60d0336b3839b9b

Author: ddupg

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

@@ -112,7 +112,7 @@ private void loadBuffers(
     }
     checkArgument(nodes.hasNext(), "no more field nodes for field %s and vector %s", field, vector);
     ArrowFieldNode fieldNode = nodes.next();
-    // variadicBufferLayoutCount will be 0 for vectors of a type except BaseVariableWidthViewVector
+    // Only view storage has variadic buffers.
     long variadicBufferLayoutCount = 0;
     if (storageVector instanceof BaseVariableWidthViewVector) {
       if (variadicBufferCounts.hasNext()) {

vector/src/main/java/org/apache/arrow/vector/extension/JsonVector.java

@@ -81,29 +81,7 @@ public TransferPair getTransferPair(
 
   @Override
   public TransferPair makeTransferPair(ValueVector target) {
-    JsonVector to = (JsonVector) target;
-    TransferPair storagePair = getUnderlyingVector().makeTransferPair(to.getUnderlyingVector());
-    return new TransferPair() {
-      @Override
-      public void transfer() {
-        storagePair.transfer();
-      }
-
-      @Override
-      public void splitAndTransfer(int startIndex, int length) {
-        storagePair.splitAndTransfer(startIndex, length);
-      }
-
-      @Override
-      public JsonVector getTo() {
-        return to;
-      }
-
-      @Override
-      public void copyValueSafe(int fromIndex, int toIndex) {
-        storagePair.copyValueSafe(fromIndex, toIndex);
-      }
-    };
+    return new TransferImpl((JsonVector) target);
   }
 
   @Override
@@ -115,4 +93,34 @@ public int hashCode(int index) {
   public int hashCode(int index, ArrowBufHasher hasher) {
     return getUnderlyingVector().hashCode(index, hasher);
   }
+
+  private class TransferImpl implements TransferPair {
+    private final JsonVector to;
+    private final TransferPair storagePair;
+
+    TransferImpl(JsonVector to) {
+      this.to = to;
+      this.storagePair = getUnderlyingVector().makeTransferPair(to.getUnderlyingVector());
+    }
+
+    @Override
+    public void transfer() {
+      storagePair.transfer();
+    }
+
+    @Override
+    public void splitAndTransfer(int startIndex, int length) {
+      storagePair.splitAndTransfer(startIndex, length);
+    }
+
+    @Override
+    public JsonVector getTo() {
+      return to;
+    }
+
+    @Override
+    public void copyValueSafe(int fromIndex, int toIndex) {
+      storagePair.copyValueSafe(fromIndex, toIndex);
+    }
+  }
 }