这个问题在这里已经有答案了：

java.sql.sqlexception:拒绝用户“root”@“localhost”的访问（使用密码：yes）（24个答案）
去年关门了。
请帮助解决此错误。同样的代码在windows中运行良好。但我不明白为什么它不能在linux（Ubuntu18.04）上运行。
以下代码：

import java.sql.*;
public class HelloWorld {

    public static void main(String[] args) {
        Connection con = null;
        Statement st = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb","root","root");
            String sql = "insert into mytable values('amsing@gmail.com','amit1234')";
            st = con.createStatement();
            int x = st.executeUpdate(sql);
            if(x==1) {
                System.out.println("Record inserted");
            }else {
                System.out.println("Record not inserted");
            }
        }catch(Exception e) {
            e.printStackTrace();
        }finally {
            try {
                if(st!=null)st.close();
                if(con!=null)con.close();
            }catch(Exception e) {
                e.printStackTrace();
            }
        }
    }  
}

运行代码时引发此异常：

Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
Sat Jul 07 12:52:40 IST 2018 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
java.sql.SQLException: Access denied for user 'root'@'localhost'
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:127)
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:95)
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
    at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:862)
    at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:444)
    at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:230)
    at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:226)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:247)
    at com.amitsingh.HelloWorld.main(HelloWorld.java:10)