Access denied for user ''@'localhost' (using password: NO) in Eclipse, instead of 'root'@'localhost', classpath corrupted [duplicate]

I'm making a java project with SceneBuilder and Eclipse; i need to connect to a local database created using MySQL, but after running my Java code in eclipse i get the following error:

Exception in thread "main" java.sql.SQLException: Access denied for user ''@'localhost' (using password: NO)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:836)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:456)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:197)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at com.mysql.cj.jdbc.admin.TimezoneDump.main(TimezoneDump.java:70)

Instead of 'root'@'localhost' (using password: NO) that is a login credentials error, now i have ''@'localhost' (using password: NO). Using MySQL workbench and command prompt, i can correctly access using "root"/"root", and launch queries on my db. Running the same Eclipseproject on another laptop or my home pc, i can run it without errors. So the problem is not in the code but in some setting of my current laptop.

I already tried to:

• Uninstall and reinstall Eclipse.
• Uninstall and reinstall mySQL products: Workbench, Server, J Connector.
• Switch Eclipse workspace.
• Open the 3306 port from windows firewall.

That's the part of the code where i try to connect to my db.

package model;

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



public class UserDAO {

    private static String USER = "root";
    private static String PASS = "root";
    private static String DB_URL = "jdbc:mysql://127.0.0.1:3306/beecological?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC";
    private static String DRIVER_CLASS_NAME = "com.mysql.cj.jdbc.Driver";


    public static boolean checkUsername(String username) {
        Statement stmt = null;
        Connection conn = null;
        int res = 1;

        try {

            Class.forName(DRIVER_CLASS_NAME);

            conn = DriverManager.getConnection(DB_URL, USER, PASS);

            stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);
            res = Queries.verifyUsernameAvailable(stmt, username);

            stmt.close();
            conn.close();
        }catch (Exception e) {
            e.printStackTrace();
        }

        if(res == 1) {
            return false;
        }
        return true;
    }

    public static void saveUser(User instance) {
        Statement stmt = null;
        Connection conn = null;

        try {

            Class.forName(DRIVER_CLASS_NAME);

            conn = DriverManager.getConnection(DB_URL, USER, PASS);

            stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);
            Queries.insertUser(stmt, instance);

            stmt.close();
            conn.close();
        }catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static boolean verifyLogin(User instance) {
        Statement stmt = null;
        Connection conn = null;
        int res = 0;

        try {
            //caricamento driver mysql
            Class.forName(DRIVER_CLASS_NAME);

            conn = DriverManager.getConnection(DB_URL, USER, PASS);

            stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);
            res = Queries.verifyUserRegistered(stmt, instance);

            stmt.close();
            conn.close();
        }catch (Exception e) {
            e.printStackTrace();
        }

        if (res == 0) {
            return false;   //utente immesso non esiste
        }
        return true;
    }
}