收到错误：“无法创建与数据库服务器的连接”

Question

出现此错误：

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
    at com.mysql.jdbc.Util.getInstance(Util.java:387)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:917)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:896)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:885)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:860)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2330)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2083)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:806)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:410)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:328)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:247)
    at database.DBConnection.getConnection(DBConnection.java:29)
    at recordSystemMain.MainLoginController.isValidCredentials(MainLoginController.java:122)
    at recordSystemMain.MainLoginController.loginButtonClick(MainLoginController.java:73)
    ... 58 more

我不明白为什么会这样！ 我在JDBC连接类中找不到任何错误

package database;

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

/

public class DBConnection {
    private Connection connection;
    private String url = "jdbc:mysql://localhost:3305/uiustudentrecordsystem?verifyServerCertificate=false&useSSL=true";
    private String user = "root";
    private String pass = "1234";

    public Connection getConnection() throws SQLException {
        connection = DriverManager.getConnection(url,user,pass);
        return connection;
    }

}

我检查了MySQL，数据库肯定存在。如果数据库存在，那么为什么没有发生连接？

但是，仍然没有建立连接