Dúvida com o comando INSERT no banco hsqldb - RESOLVIDO

package project;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Scanner;

/**
 * Title:        Testdb
 * Description:  simple hello world db example of a
 *               standalone persistent db application
 *
 *               every time it runs it adds four more rows to sample_table
 *               it does a query and prints the results to standard out
 *
 * Author: Karl Meissner [email removido]
 */
public class MainProject {
	private static Scanner leitor = new Scanner(System.in);
	
    Connection conn;  //our connnection to the db - presist for life of program
	private String opcao;

    // we dont want this garbage collected until we are done
    public MainProject(String db_file_name_prefix) throws Exception {    // note more general exception

        // Load the HSQL Database Engine JDBC driver
        // hsqldb.jar should be in the class path or made part of the current jar
        Class.forName("org.hsqldb.jdbcDriver");

        // connect to the database.   This will load the db files and start the
        // database if it is not alread running.
        // db_file_name_prefix is used to open or create files that hold the state
        // of the db.
        // It can contain directory names relative to the
        // current working directory
        conn = DriverManager.getConnection("jdbc:hsqldb:"
                                           + db_file_name_prefix,    // filenames
                                           "sa",                     // username
                                           "");                      // password
    }

    public void shutdown() throws SQLException {

        Statement st = conn.createStatement();

        // db writes out to files and performs clean shuts down
        // otherwise there will be an unclean shutdown
        // when program ends
        st.execute("SHUTDOWN");
        conn.close();    // if there are no other open connection
    }

//use for SQL command SELECT
    public synchronized void query(String expression) throws SQLException {

        Statement st = null;
        ResultSet rs = null;

        st = conn.createStatement();         // statement objects can be reused with

        // repeated calls to execute but we
        // choose to make a new one each time
        rs = st.executeQuery(expression);    // run the query

        // do something with the result set.
        dump(rs);
        st.close();    // NOTE!! if you close a statement the associated ResultSet is

        // closed too
        // so you should copy the contents to some other object.
        // the result set is invalidated also  if you recycle an Statement
        // and try to execute some other query before the result set has been
        // completely examined.
    }

//use for SQL commands CREATE, DROP, INSERT and UPDATE
    public synchronized void update(String expression) throws SQLException {

        Statement st = null;

        st = conn.createStatement();    // statements

        int i = st.executeUpdate(expression);    // run the query

        if (i == -1) {
            System.out.println("db error : " + expression);
        }

        st.close();
    }    // void update()

    public static void dump(ResultSet rs) throws SQLException {

        // the order of the rows in a cursor
        // are implementation dependent unless you use the SQL ORDER statement
        ResultSetMetaData meta   = rs.getMetaData();
        int               colmax = meta.getColumnCount();
        int               i;
        Object            o = null;

        // the result set is a cursor into the data.  You can only
        // point to one row at a time
        // assume we are pointing to BEFORE the first row
        // rs.next() points to next row and returns true
        // or false if there is no next row, which breaks the loop
        for (; rs.next(); ) {
            for (i = 0; i < colmax; ++i) {
                o = rs.getObject(i + 1);    // Is SQL the first column is indexed

                // with 1 not 0
                System.out.print(o.toString() + " ");
            }

            System.out.println(" ");
        }
    }                                       // void dump( ResultSet rs )

    public static void main(String[] args) {
    	String opcao;
        MainProject db = null;

        try {
            db = new MainProject("db_file.db");
        } catch (Exception ex1) {
            ex1.printStackTrace();    // could not start db
            return;                   // bye bye
        }

        try {

            //make an empty table
            //
            // by declaring the id column IDENTITY, the db will automatically
            // generate unique values for new rows- useful for row keys
            db.update(
                "CREATE TABLE sample_table ( id INTEGER IDENTITY, str_col VARCHAR(256), num_col INTEGER)");
        } catch (SQLException ex2) {

            //ignore
            //ex2.printStackTrace();  // second time we run program
            //  should throw execption since table
            // already there
            //
            // this will have no effect on the db
        }
        try {           	
        	
    		do{
    			System.out.println("\n1. Cadastrar Carro e Kilometragem:");
    			System.out.println("2. Listar os carros cadastrados:");
    			System.out.println("3. Sair");
    			System.out.println("\nEscolha a opçao desejada:");
    			opcao = leitor.nextLine();
    			
    			if(opcao.equals("1")){
    				//cadastrar um carro e a kilometragem total do carro
            		String nome;
            		String quilometragem;
            		
        			System.out.println("Qual o nome do carro?");
        			nome = leitor.nextLine();            		
            		
        			System.out.println("Qual o Quilometragem do carro?");
        			quilometragem = leitor.nextLine();
        			
            		//*********** DUVIDA NO INSERT *******************
        			// Quero salvar no banco o conteúdo das variáveis
 
                    db.update(
                    "INSERT INTO sample_table(str_col,num_col) VALUES('nome', 100)");
                                                                    // nome, quilometragem
                    //************************************************
                    
                    
    			}else if(opcao.equals("2")){   				
                	// listar o conteúdo da tabela
                    System.out.println("Dados inseridos com sucesso!\n\n");      
                    // do a query
                    System.out.println("DADOS CONTIDOS NA TABELA:\n");
                    db.query("SELECT * FROM sample_table");
                    
                    
    			}else if(opcao.equals("3")){ 				
                    // SAIR DO PROGRAMA
                    db.shutdown();
                    
    			}else{
    				System.out.println("\nOpção Invalida!!!");
    			}
    		} while (!opcao.equals("3"));
    			
         } catch (SQLException ex3) {
            ex3.printStackTrace();
         }
         
    }    // fim da main()	
}    // fim da classe Testdb