javadio

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JBDC
{
    private Connection connection =null;

    public void connect()
    {
        String dbname = "Gym";
        String username = "postgres";
        String password = "199292";

        try
        {
        connection = DriverManager.getConnection("jdbc:postgresql://localhost:5432/" + dbname,username, password);
        }
        catch (SQLException e) {
        System.err.println("Connection Failed!"); e.printStackTrace();
        return;
        }
        if (connection != null) {
        System.out.println("Connection successful"); } else
        { }
        System.err.println("Failed to make connection!");

    }

    public void close()
    {
        try
        {
        connection.close(); System.out.println("Connection closed");
        }
        catch (SQLException e) {
                            e.printStackTrace();
        System.out.println("Connection could not be closed – SQL exception");
        }
    }

    public void executeQuery ()
    {
        Statement stmt = null;
        String query = " SELECT * FROM course";
        try {
        stmt = connection.createStatement(); ResultSet rs = stmt.executeQuery(query);
        //the next method of ResultSet allows you to iterate through the results
        while (rs.next())
        {
        // the getString method of the ResultSet object allows you to access the value for the given column name for the current row in the result set as a String. If the value is an integer you can use getInt(“col_name”)
                                  String course_name = rs.getString("name");
        System.out.println(course_name); }
        }
        catch (SQLException e ) {
        e.printStackTrace();
        System.err.println("error executing query " + query);
        }
    }

}