java如何连接数据库

Java可以使用JDBC(Java Database Connectivity) API连接数据库。开发者需要使用JDBC驱动程序来连接不同的数据库，例如MySQL、Oracle、SQL Server等等。下面是一个连接MySQL数据库的示例代码：

import java.sql.*;

public class JDBCDemo {
    static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    static final String DB_URL = "jdbc:mysql://localhost:3306/test";
    static final String USER = "root";
    static final String PASS = "123456";

    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            Class.forName(JDBC_DRIVER);
            System.out.println("连接数据库...");
            conn = DriverManager.getConnection(DB_URL, USER, PASS);
            System.out.println("实例化Statement对象...");
            stmt = conn.createStatement();
            String sql;
            sql = "SELECT id, name, age FROM student";
            ResultSet rs = stmt.executeQuery(sql);
            while(rs.next()){
                int id  = rs.getInt("id");
                String name = rs.getString("name");
                int age = rs.getInt("age");
                System.out.print("ID: " + id);
                System.out.print(", 姓名: " + name);
                System.out.println(", 年龄: " + age);
            }
            rs.close();
            stmt.close();
            conn.close();
        } catch (SQLException se) {
            se.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (stmt != null) stmt.close();
            } catch (SQLException se2) {
            }
            try {
                if (conn != null) conn.close();
            } catch (SQLException se) {
                se.printStackTrace();
            }
        }
        System.out.println("Goodbye!");
    }
}