HSQLDB inmemory mode doesn't delete files on shutdown

I'm using HSQLDB version 2.2.9 for testing purposes. When I create named in memory database, files aren't deleted after calling shutdown function. On my filesystem I have folder DBname.tmp and files DBname.lck, DBname.log, DBname.properties and DBname.script. As I understand documentation (http://hsqldb.org/doc/2.0/guide/dbproperties-chapt.html#dpc_connection_url) it shouldn't happened.
For testing I'm using the following code:


import java.io.IOException;
import org.hsqldb.Server;
import org.hsqldb.persist.HsqlProperties;
import org.hsqldb.server.ServerAcl.AclFormatException;
import org.junit.Test;

public class HSQLDBInMemTest {

@Test
public void test() throws IOException, AclFormatException {
HsqlProperties props = new HsqlProperties();
props.setProperty("server.database.0", "test1");
props.setProperty("server.dbname.0", "test1");

props.setProperty("server.database.1", "test2");
props.setProperty("server.dbname.1", "test2");
Server hsqlServer = new Server();
hsqlServer.setRestartOnShutdown(false);
hsqlServer.setNoSystemExit(true);
hsqlServer.setProperties(props);
hsqlServer.start();
hsqlServer.shutdown();
}
}

I asked this question originally here: http://stackoverflow.com/questions/16694067/hsqldb-inmemory-mode-doesnt-delete-files-on-shutdown

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