[JAVA] aplikasi bbm

/**
 * Write a description of class pertaminaapp here.
 *
 * @author (ti)
 * @version (a version number or a date)
 */
import java.sql.*;
import java.io.*;
import java.util.*;

public class pertaminaapp
{
    static String jdbc_driver   ="com.mysql.jdbc.Driver";
    static String db_host       ="jdbc:mysql://localhost/db_pertamina";
    static String db_user       ="root";
    static String db_pass       ="12345678";

    static Connection conn=null;
    static Statement stmt=null;
    static ResultSet rs=null;

    static Scanner inputanSC = new Scanner(System.in);
    static InputStreamReader inputStreamReader = new InputStreamReader(System.in);
    static BufferedReader inputanBR = new BufferedReader(inputStreamReader);

    static void bukaKoneksiDb() throws IOException{
        try{
            Class.forName(jdbc_driver);
            conn = DriverManager.getConnection(db_host,db_user,db_pass);
            stmt=conn.createStatement();
            //System.out.print("buka koneksi berhasil");
        }
        catch(Exception e){
            System.err.print("buka koneksi gagal "+e.getMessage());

        }

    }

    static void tutupKoneksiDb() throws IOException{
        try{
            conn.close();
            stmt.close();
        }
        catch(Exception e){
            System.err.print("gagal tutup "+e.getMessage());

        }

    }

    static void lihatSmuadata() throws IOException{
        String query;
        try{
            bukaKoneksiDb();
            query ="SELECT * from bahan_bakar" ;
            //ResultSet rowData;
            rs = stmt.executeQuery(query);
            System.out.println();
            System.out.println("| ID  | jenis bahanbakar | RON | harga |");

            //if (rs.next()==true){
                //System.out.print("ada");
                while(rs.next()){
                    //id`, `jenis_bahanbakar`, `ron`, `harga
                    System.out.println("| "+rs.getInt("id")+" | "+rs.getString("jenis_bahanbakar")+"| "+rs.getString("ron")+"|"+rs.getString("harga")+"");
                }
            //}else{
                //System.out.print("tdk ada data");
            //}

            tutupKoneksiDb();
        }

        catch(Exception e){
            System.err.print("ada yang salah nih! "+e.getMessage());
            e.printStackTrace();

        }

    }

    static void pencarianId(int var_id) throws IOException{
        String query1;
        try{
            bukaKoneksiDb();
            query1 ="SELECT * from bahan_bakar WHERE id="+var_id;
            ResultSet rowData;
            rowData = stmt.executeQuery(query1);
            System.out.println();

            if (rowData.next()==true){
                //System.out.print("ada");
                //id`, `jenis_bahanbakar`, `ron`, `harga
                System.out.println("id               :"+rowData.getString("id"));
                System.out.println("jenis bahanbakar :"+rowData.getString("jenis_bahanbakar"));
                System.out.println("ron              :"+rowData.getString("ron"));
                System.out.println("harga perliter   :"+rowData.getString("harga"));
            }else{
                System.out.print("tdk ada data");
            }

            tutupKoneksiDb();
        }

        catch(Exception e){
            System.err.print("ada yang salah nih! "+e.getMessage());
            e.printStackTrace();

        }

    }

    static int pembelianBBM(int var_id,int var_liter) throws IOException{
        String query2;
        int total_bayar=0;
        int hrgPerliter=0;
        try{
            bukaKoneksiDb();
            query2 ="SELECT * from bahan_bakar WHERE id="+var_id;
            ResultSet rowData;
            rowData = stmt.executeQuery(query2);
            System.out.println();

            if (rowData.next()==true){
                //System.out.print("ada");
                //id`, `jenis_bahanbakar`, `ron`, `harga
                hrgPerliter=rowData.getInt("harga");
                total_bayar=hrgPerliter*var_liter;
            }else{
                System.out.print("tdk ada data");
            }

             tutupKoneksiDb();
        }

        catch(Exception e){
            System.err.print("ada yang salah nih! "+e.getMessage());
            e.printStackTrace();

        }
        return total_bayar;


    }

    public static void main (String [] args){

        try{
            lihatSmuadata();
            System.out.println();
            System.out.print("cari id bahan bakar :");
            int input_id = inputanSC.nextInt();
            //String input_id = inputanSC.nextLine();
            //int ivar_id = Integer.parseInt(input_id);
            //System.out.print("id = "+input_id);
            pencarianId(input_id);

            /*String input_id = inputanBR.readLine();
            int ivar_id = Integer.parseInt(input_id);
            pencarianId(ivar_id);
             */
            System.out.println();
            System.out.println("Pembelian BBM");
            System.out.print("BBM(101/102/103/104 -> (ID)liat diatas) :");
            int input_id2 = inputanSC.nextInt();
            System.out.print("Beli(liter) :");
            int input_liter = inputanSC.nextInt();
            int uangkeluar = pembelianBBM(input_id2,input_liter);
            System.out.print("anda harus membayar :"+uangkeluar);
        }
        catch(Exception e){
            System.err.print("ada yang salah nih! "+e.getMessage());
            e.printStackTrace();

        }

    }
}