Addressed comments

Author: sakthivelmanii

google-cloud-spanner/src/main/java/com/google/cloud/spanner/DatabaseClientImpl.java

@@ -46,8 +46,6 @@ class DatabaseClientImpl implements DatabaseClient {
   @VisibleForTesting final boolean useMultiplexedSessionPartitionedOps;
   @VisibleForTesting final boolean useMultiplexedSessionForRW;
 
-  private StatementFactory statementFactory = null;
-
   final boolean useMultiplexedSessionBlindWrite;
 
   @VisibleForTesting

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerTypeConverter.java

@@ -98,7 +98,7 @@ static <T> Value createUntypedIterableValue(
   }
 
   static ZonedDateTime atUTC(LocalDateTime localDateTime) {
-    return localDateTime.atZone(UTC_ZONE);
+    return atUTC(localDateTime.atZone(ZoneId.systemDefault()));
   }
 
   static ZonedDateTime atUTC(OffsetDateTime localDateTime) {

google-cloud-spanner/src/main/java/com/google/cloud/spanner/Statement.java

@@ -249,6 +249,34 @@ StringBuilder toString(StringBuilder b) {
     return b;
   }
 
+  /**
+   * Factory for creating {@link Statement}.
+   *
+   * <p>This factory class supports creating {@link Statement} with positional(or unnamed)
+   * parameters.
+   *
+   * <p>
+   *
+   * <h2>Usage Example</h2>
+   *
+   * Simple SQL query
+   *
+   * <pre>{@code
+   * Statement statement = databaseClient.getStatementFactory()
+   *     .withUnnamedParameters("SELECT * FROM TABLE WHERE ID = ?", 10L)
+   * }</pre>
+   *
+   * How to use SQL queries with IN command
+   *
+   * <pre>{@code
+   * long[] ids = {10L, 12L, 1483L};
+   * Statement statement = databaseClient.getStatementFactory()
+   *     .withUnnamedParameters("SELECT * FROM TABLE WHERE ID = UNNEST(?)", ids)
+   * }</pre>
+   *
+   * @see DatabaseClient#getStatementFactory()
+   * @see StatementFactory#withUnnamedParameters(String, Object...)
+   */
   public static final class StatementFactory {
     private final Dialect dialect;
 
@@ -262,7 +290,7 @@ public Statement of(String sql) {
 
     /**
      * This function accepts the SQL statement with unnamed parameters(?) and accepts the list of
-     * objects to replace unnamed parameters. Primitive types are supported
+     * objects to replace unnamed parameters. Primitive types are supported.
      *
      * <p>For Date column, following types are supported
      *

google-cloud-spanner/src/main/java/com/google/cloud/spanner/Value.java

@@ -50,7 +50,6 @@
 import java.time.LocalDate;
 import java.time.LocalDateTime;
 import java.time.OffsetDateTime;
-import java.time.ZoneId;
 import java.time.ZonedDateTime;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -871,13 +870,10 @@ static Value toValue(Object value) {
       return Value.date(convertLocalDateToSpannerDate((LocalDate) value));
     }
     if (value instanceof LocalDateTime) {
-      return createUntypedStringValue(
-          convertToISO8601(
-              SpannerTypeConverter.atUTC(((LocalDateTime) value).atZone(ZoneId.systemDefault()))));
+      return createUntypedStringValue(convertToISO8601(atUTC((LocalDateTime) value)));
     }
     if (value instanceof OffsetDateTime) {
-      return createUntypedStringValue(
-          convertToISO8601(SpannerTypeConverter.atUTC((OffsetDateTime) value)));
+      return createUntypedStringValue(convertToISO8601(atUTC((OffsetDateTime) value)));
     }
     if (value instanceof ZonedDateTime) {
       return createUntypedStringValue(convertToISO8601(atUTC((ZonedDateTime) value)));
@@ -945,16 +941,11 @@ static Value toValue(Object value) {
       }
       if (object instanceof LocalDateTime) {
         return createUntypedIterableValue(
-            (LocalDateTime) object,
-            iterator,
-            val ->
-                convertToISO8601(SpannerTypeConverter.atUTC(val.atZone(ZoneId.systemDefault()))));
+            (LocalDateTime) object, iterator, val -> convertToISO8601(atUTC(val)));
       }
       if (object instanceof OffsetDateTime) {
         return createUntypedIterableValue(
-            (OffsetDateTime) object,
-            iterator,
-            val -> convertToISO8601(SpannerTypeConverter.atUTC(val)));
+            (OffsetDateTime) object, iterator, val -> convertToISO8601(atUTC(val)));
       }
       if (object instanceof ZonedDateTime) {
         return createUntypedIterableValue(