错误 - 无法找到或加载主类

我想连接我的java程序来连接数据库并检索数据。 它编译完美，但运行时 我明白了Error : Could not find or load main class

我已经安装了Java SQL驱动程序并将jar路径添加到环境变量作为CLASSPATH

import java.sql.*;
public class Java2Sql{
    public static void main(String args[]){
        String url = "jdbc:mysql://localhost:80/";
        String dbName = "test";
        String driver = "com.mysql.jdbc.Driver";
        String userName = "root";
        String password = "root";

        try{
            Class.forName(driver).newInstance();
            Connection conn = DriverManager.getConnection(url+dbName,userName,password);

            Statement stmt = conn.createStatement();
            String strsql = "SELECT * FROM student";

            ResultSet res = stmt.executeQuery(strsql);

            while(res.next()){
                System.out.println("ID :"+res.getString(1));
                System.out.println("Name :"+res.getString(2));
                System.out.println("Tel :"+res.getString(3));
                System.out.println("City :"+res.getString(4));
            }
            res.close();
            conn.close();
        }catch(Exception e){
            e.printStackTrace();
        }

    }
}

比方说你的Java2Sql在里面test包裹。

文件夹结构：

您尝试运行的代码如下。

Code:

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

public class Java2Sql {
    public static void main(String args[]) {
        Connection connection = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            connection = DriverManager.getConnection(
            "jdbc:mysql://localhost:3306/test", "username", "pwd"); // Test DB
            System.out.println("Connected.");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }

    }
}

您需要编译和运行的命令是：

javac Java2Sql.java
java -classpath .;test/mysql-connector-java-5.0.4-bin.jar test.Java2Sql

编译与执行：