java连接数据库实现增删改查

import java.sql.*;

public class JDBCDemo {
    // 数据库URL、用户名和密码
    static final String JDBC_DRIVER = "com.mysql.cj.jdbc.Driver";
    static final String DB_URL = "jdbc:mysql://localhost/EMP";
    static final String USER = "username";
    static final String PASS = "password";

    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            // 注册JDBC驱动
            Class.forName(JDBC_DRIVER);

            // 打开连接
            System.out.println("连接数据库...");
            conn = DriverManager.getConnection(DB_URL, USER, PASS);

            // 执行查询
            System.out.println("实例化Statement对象...");
            stmt = conn.createStatement();
            String sql;
            sql = "SELECT id, first, last, age FROM Employees";
            ResultSet rs = stmt.executeQuery(sql);

            // 展开结果集数据库
            while (rs.next()) {
                // 通过列名获取
                int id = rs.getInt("id");
                int age = rs.getInt("age");
                String first = rs.getString("first");
                String last = rs.getString("last");

                // 显示结果
                System.out.print("ID: " + id);
                System.out.print(", Age: " + age);
                System.out.print(", First: " + first);
                System.out.println(", Last: " + last);
            }
            // 关闭连接
            rs.close();
            stmt.close();
            conn.close();
        } catch (SQLException se) {
            // 处理JDBC错误
            se.printStackTrace();
        } catch (Exception e) {
            // 处理Class.forName错误
            e.printStackTrace();
        } finally {
            // 关闭资源
            try {
                if (stmt != null) stmt.close();
            } catch (SQLException se2) {
            } // 什么都不做
            try {
                if (conn != null) conn.close();
            } catch (SQLException se) {
                se.printStackTrace();
            }
        }
        System.out.println("Goodbye!");
    }
}