CQLSSTableWriter: close does not work + more than one table throws ex

import org.apache.cassandra.config.Config;
import org.apache.cassandra.io.sstable.CQLSSTableWriter;

public static void main(String[] args) {
  Config.setClientMode(true);

  CQLSSTableWriter w1 = CQLSSTableWriter.builder()
    .inDirectory("/tmp/kspc/t1")
    .forTable("CREATE TABLE kspc.t1 ( id  int, PRIMARY KEY (id));")
    .using("INSERT INTO kspc.t1 (id) VALUES ( ? );")
    .build();

  CQLSSTableWriter w2 = CQLSSTableWriter.builder()
    .inDirectory("/tmp/kspc/t2")
    .forTable("CREATE TABLE kspc.t2 ( id  int, PRIMARY KEY (id));")
    .using("INSERT INTO kspc.t2 (id) VALUES ( ? );")
    .build();

  try {
    w1.addRow(1);
    w2.addRow(1);
    w1.close();
    w2.close();
  } catch (Exception e) {
    System.out.println(e);
  }
}

Exception in thread "main" java.lang.ExceptionInInitializerError
        at org.apache.cassandra.db.Keyspace.initCf(Keyspace.java:324)
        at org.apache.cassandra.db.Keyspace.<init>(Keyspace.java:277)
        at org.apache.cassandra.db.Keyspace.open(Keyspace.java:119)
        at org.apache.cassandra.db.Keyspace.open(Keyspace.java:96)
        at org.apache.cassandra.cql3.statements.UpdateStatement.addUpdateForKey(UpdateStatement.java:101)
        at org.apache.cassandra.io.sstable.CQLSSTableWriter.rawAddRow(CQLSSTableWriter.java:226)
        at org.apache.cassandra.io.sstable.CQLSSTableWriter.addRow(CQLSSTableWriter.java:145)
        at org.apache.cassandra.io.sstable.CQLSSTableWriter.addRow(CQLSSTableWriter.java:120)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoCachedMethodSite.invoke(PojoMetaMethodSite.java:189)
        at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:53)
        at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:120)
        at com.allthingsmonitoring.utils.BulkDataLoader.main(BulkDataLoader.groovy:415)
Caused by: java.lang.NullPointerException
        at org.apache.cassandra.config.DatabaseDescriptor.getFlushWriters(DatabaseDescriptor.java:1053)
        at org.apache.cassandra.db.ColumnFamilyStore.<clinit>(ColumnFamilyStore.java:85)
        ... 18 more