DBConnection.java

import java.sql.*;
import java.util.Properties;

public class DBConnection {

    private Connection connect = null;
    private Statement statement = null;
    private ResultSet resultSet = null;

    private static String URL = "jdbc:mysql://localhost:3306/QA28";
    private static String USER = "root";
    private static String PASSWORD = "Password001!";

    public void connect() {
        Properties properties = new Properties();
        properties.setProperty("user", USER);
        properties.setProperty("password", PASSWORD);
        properties.setProperty("allowPublicKeyRetrieval", "true");
        try {
            connect = DriverManager.getConnection(URL, properties);
            statement = connect.createStatement();
            System.out.println("Соеденение с БД выполнено");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public ResultSet select(String query) {
        try {
            return statement.executeQuery(query);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    public void insert(String query) {
        try {
            statement.execute(query);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public void insertPrepared(String name) {
        try {
            PreparedStatement statement1 = connect.prepareStatement("INSERT INTO students(name) VALUES (?)");
            statement1.setString(1, name);
            statement1.execute();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public void delete(String query) {
        try {
            statement.execute(query);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public void close() {
        try {
            if (connect != null) {
                connect.close();
                System.out.println("Соеденение с БД закрыто");
            }
            if (statement != null) {
                statement.close();
            }
            if (resultSet != null) {
                resultSet.close();
            }
        } catch (Exception ignored) {

        }
    }
}

DBTest.java

import org.testng.annotations.Test;

import java.sql.ResultSet;
import java.sql.SQLException;

public class DBTest {

    @Test
    public void checkDB() throws SQLException {
        String name = "blabla'); DELETE FROM students;";
        DBConnection connection = new DBConnection();
        connection.connect();
//        connection.insert("INSERT INTO students (name) VALUES ('blabla')')");
        connection.insertPrepared("Borodich Timofei");
        ResultSet result = connection.select("SELECT * FROM students");
        while (result.next()) {
            System.out.println(result.getInt("id"));
            System.out.println(result.getString("name"));
            System.out.println(result.getInt("group_id"));
        }
        connection.delete("DELETE FROM students WHERE name = 'Timofei Borodich'");
        connection.close();
    }
}