Can't connect to oracle db

could you pls help give me advice i try connect to oracle database but getting error like below ?

Cannot cast object ‘oracle.jdbc.driver.T4CConnection@45792847’ with class ‘oracle.jdbc.driver.T4CConnection’ to class ‘com.mysql.jdbc.Connection’

below my connection :

package com.database
import java.sql.DriverManager
import java.sql.ResultSet

import com.kms.katalon.core.annotation.Keyword
import com.mysql.jdbc.Connection
import com.mysql.jdbc.Statement

import oracle.jdbc.*

public class mysql {

private static Connection connection = null;

/**
 * Open and return a connection to database
 * @param dataFile absolute file path
 * @return an instance of java.sql.Connection
 */

//Establishing a connection to the DataBase

@Keyword

def connectDB (String url, String port, String dbname, String username, String password){

	String conn = "jdbc:oracle:thin:@//" + url + ":" + port + "/" + dbname

	if(connection != null && !connection.isClosed()){

		connection.close()

	}

	connection = DriverManager.getConnection(conn, username, password)

	return connection

}

/**
 * execute a SQL query on database
 * @param queryString SQL query string
 * @return a reference to returned data collection, an instance of java.sql.ResultSet
 */

//Executing the constructed Query and Saving results in resultset

@Keyword

def executeQuery(String queryString) {

	Statement stm = connection.createStatement()

	ResultSet rs = stm.executeQuery(queryString)

	return rs

}

//Closing the connection

@Keyword

def closeDatabaseConnection() {

	if(connection != null && !connection.isClosed()){

		connection.close()

	}

	connection = null

}

/**
 * Execute non-query (usually INSERT/UPDATE/DELETE/COUNT/SUM...) on database
 * @param queryString a SQL statement
 * @return single value result of SQL statement
 */

@Keyword

def execute(String queryString) {

	Statement stm = connection.createStatement()

	boolean result = stm.execute(queryString)

	return result

}

}