Java-what should I do if the resultset object obtained by the second SQL statement is null?

PublicListgetAll1 (Stringname) throwsException {ListresultnewArrayList (); ConnectionconDatabaseConnection. getConnection (); Stringnanull; Stringsql1 & quot; select * fromguanzhuwhereguanzhu? & Quot; PreparedStatementps1con. prepareS java database mysql computer jsp

Public ListgetAll1 (String name) throws Exception {

Listresult = new ArrayList ();

Connection con = DatabaseConnection. getConnection ();

String na = null;

String sql1 = "select * from guanzhu where guanzhu =? ";

PreparedStatement ps1 = con. prepareStatement (sql1 );

Ps1.setString (1, name );

ResultSet rs1 = ps1.executeQuery ();

While (rs1.next ()){

Connection con1 = DatabaseConnection. getConnection ();

Na = rs1.getString ("beiguanzhu ");

String SQL = "select * from message where author =? Order by modified desc "; PreparedStatement ps = con1.prepareStatement (SQL );

Ps. setString (1, na); ResultSet rs = ps.exe cuteQuery ();

While (rs. next ()){

Message m = new Message ();

M. setId (rs. getInt ("id "));

M. setTitle (rs. getString ("title "));

M. setContent (rs. getString ("content "));

M. setModified (rs. getDate ("modified "));

M. setAuthor (rs. getString ("author "));

Result. add (m );

System. out. println (rs. getString ("author") + "");

}

}

Return result;
}