Main

package test;

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

public class Main {

    public static void main(String[] args) {

        try (Connection connection = DriverManager.getConnection("jdbc:postgresql://localhost:5433/postgres","postgres", "Vietnammechkey 771993")) {

            System.out.println("Connected to PostgreSQL database!");
            Statement stmt = connection.createStatement();
            ResultSet rs = stmt.executeQuery("SELECT username FROM mstuser WHERE userid='1'");
            while (rs.next()) {
                  String username = rs.getString("username");
                  System.out.println(username + "\n");
                }
        }

        catch (SQLException e) {
            System.out.println("Connection failure.");
            e.printStackTrace();
        }
    }
}