java怎么读取数据库数据

```java

import java.sql.*;

public class ReadDataFromDatabase {

public static void main(String[] args) {

String url = "jdbc:mysql://localhost:3306/mydatabase";

String username = "root";

String password = "password";

try {

Connection conn = DriverManager.getConnection(url, username, password);

Statement stmt = conn.createStatement();

ResultSet rs = stmt.executeQuery("SELECT * FROM mytable");

while (rs.next()) {

int id = rs.getInt("id");

String name = rs.getString("name");

double price = rs.getDouble("price");

System.out.println("ID: " + id + ", Name: " + name + ", Price: " + price);

}

rs.close();

stmt.close();

conn.close();

} catch (SQLException e) {

e.printStackTrace();

}

}

}

```

在上面的代码中，首先通过`DriverManager.getConnection()`方法来建立与数据库的连接，然后创建一个`Statement`对象来执行SQL查询语句，接着通过`ResultSet`对象来遍历查询结果并读取数据。最后记得关闭所有的资源，包括`ResultSet`、`Statement`和`Connection`。