create table TEST (dvalue number( 15 , 4 ));

create or replace and compile java source named "DoubleTest" as
 import  java.sql.*;

 public   class  DoubleTest {

   public   static   void  foo()
     throws  Exception {
    Connection con =  null ;
    Statement st =  null ;
    PreparedStatement pst =  null ;
     try  {
      con = DriverManager.getConnection("jdbc:default:connection:");

      pst = con.prepareStatement("insert into TEST (dvalue) values (?)");

      st = con.createStatement();

      st.execute("alter session set nls_numeric_characters=', '");
      pst.setDouble( 1 ,  Double .parseDouble("5.05"));
      pst.execute();

      st.execute("alter session set nls_numeric_characters='. '");
      pst.setDouble( 1 ,  Double .parseDouble("5.05"));
      pst.execute();

      ResultSet rs = st.executeQuery("select * from TEST");
       while  (rs.next()) {
        System.out.println(rs.getDouble( 1 ));
      }
    }  finally  {
       if  (st !=  null ) { st.close();}
       if  (pst !=  null ) { pst.close();}
       if  (con !=  null ) { con.close();}
    }
  }
}
/

create or replace procedure double_test as language java name 'DoubleTest.foo()';
/

SQL> set serverout on
SQL> exec dbms_java.set_output( 20000 );

PL/SQL procedure successfully completed.

SQL> exec double_test;
 5 . 05 
 5 . 05