ARROW-3966: Using a helper method for building a UTC calendar with root locale.

Author: Mike Pigott

java/adapter/jdbc/src/main/java/org/apache/arrow/adapter/jdbc/JdbcToArrow.java

@@ -23,8 +23,6 @@
 import java.sql.SQLException;
 import java.sql.Statement;
 import java.util.Calendar;
-import java.util.Locale;
-import java.util.TimeZone;
 
 import org.apache.arrow.memory.BaseAllocator;
 import org.apache.arrow.memory.RootAllocator;
@@ -90,7 +88,7 @@ public static VectorSchemaRoot sqlToArrow(Connection connection, String query, B
     Preconditions.checkNotNull(allocator, "Memory allocator object can not be null");
 
     JdbcToArrowConfig config =
-            new JdbcToArrowConfig(allocator, Calendar.getInstance(TimeZone.getTimeZone("UTC"), Locale.ROOT), false);
+            new JdbcToArrowConfig(allocator, JdbcToArrowUtils.getUtcCalendar(), false);
     return sqlToArrow(connection, query, config);
   }
 
@@ -155,7 +153,7 @@ public static VectorSchemaRoot sqlToArrow(Connection connection, String query, J
   public static VectorSchemaRoot sqlToArrow(ResultSet resultSet) throws SQLException, IOException {
     Preconditions.checkNotNull(resultSet, "JDBC ResultSet object can not be null");
 
-    return sqlToArrow(resultSet, Calendar.getInstance(TimeZone.getTimeZone("UTC"), Locale.ROOT));
+    return sqlToArrow(resultSet, JdbcToArrowUtils.getUtcCalendar());
   }
 
   /**
@@ -172,7 +170,7 @@ public static VectorSchemaRoot sqlToArrow(ResultSet resultSet, BaseAllocator all
     Preconditions.checkNotNull(allocator, "Memory Allocator object can not be null");
 
     JdbcToArrowConfig config = 
-            new JdbcToArrowConfig(allocator, Calendar.getInstance(TimeZone.getTimeZone("UTC"), Locale.ROOT), false);
+            new JdbcToArrowConfig(allocator, JdbcToArrowUtils.getUtcCalendar(), false);
     return sqlToArrow(resultSet, config);
   }
 

java/adapter/jdbc/src/main/java/org/apache/arrow/adapter/jdbc/JdbcToArrowUtils.java

@@ -38,7 +38,9 @@
 import java.util.Calendar;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
+import java.util.TimeZone;
 
 import org.apache.arrow.memory.RootAllocator;
 import org.apache.arrow.vector.BaseFixedWidthVector;
@@ -108,6 +110,13 @@ public static Schema jdbcToArrowSchema(ResultSetMetaData rsmd, Calendar calendar
     return jdbcToArrowSchema(rsmd, new JdbcToArrowConfig(new RootAllocator(0), calendar, false));
   }
 
+  /**
+   * Returns the instance of a {java.util.Calendar} with the UTC time zone and root locale.
+   */
+  public static Calendar getUtcCalendar() {
+    return Calendar.getInstance(TimeZone.getTimeZone("UTC"), Locale.ROOT);
+  }
+
   /**
    * Create Arrow {@link Schema} object for the given JDBC {@link ResultSetMetaData}.
    *