import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class DBS {

	private Connection connection;

	public void establishConection() {

		try {
			Class.forName("org.postgresql.Driver");
		} catch (ClassNotFoundException e1) {
			// TODO Auto-generated catch block
			e1.printStackTrace();
		}

		try {
			connection = DriverManager.getConnection("jdbc:postgresql://10.152.212.116:5432/postgres", "postgres",
					"12345");
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

	public DBS() {
		establishConection();
	}

	public int getStudent(String name, String study, int subID, double grade) {
		ResultSet resultSet = null;
		int returnNumber = 0;

		try {
			String sql = " SELECT * FROM students where(name=? AND study_line=? AND subject_id=? AND average=?)";

			PreparedStatement st = connection.prepareStatement(sql);
			st.setString(1, name);
			st.setString(2, study);
			st.setInt(3, subID);
			st.setDouble(4, grade);
			resultSet = st.executeQuery();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		int studentNo;
		try {
			while (resultSet.next()) {
				studentNo = resultSet.getInt("student_no");
				returnNumber = studentNo;
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

		return returnNumber;

	}

	public static void main(String[] args) {
		DBS data = new DBS();
		System.out.println("" + data.getStudent("Angelica", "Chemical Engineering and Food Technology", 34386, 8.10));
	}

}