用eclipse写一个数据库管理系统

首先，你需要安装Eclipse和Java Development Kit（JDK）。

然后，创建一个新的Java项目。在项目中创建一个新的包，命名为“dbms”。

在“dbms”包中创建以下Java类：

1. DBConnect.java - 用于连接到数据库的类

import java.sql.Connection;
import java.sql.DriverManager;

public class DBConnect {
    // 数据库连接信息
    private static final String URL = "jdbc:mysql://localhost:3306/db_name";
    private static final String USER = "username";
    private static final String PASS = "password";

    public static Connection connect() {
        Connection conn = null;
        try {
            // 加载驱动
            Class.forName("com.mysql.jdbc.Driver");
            // 建立连接
            conn = DriverManager.getConnection(URL, USER, PASS);
            System.out.println("Connected to database successfully!");
        } catch (Exception e) {
            e.printStackTrace();
        }
        return conn;
    }
}

2. DBManager.java - 用于执行数据库操作的类

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class DBManager {

    private static Connection conn = DBConnect.connect();

    // 插入数据
    public static void insertData(String tableName, String[] data) {
        String query = "INSERT INTO " + tableName + " VALUES (";
        for (int i = 0; i < data.length; i++) {
            query += "'" + data[i] + "'";
            if (i != data.length - 1) {
                query += ",";
            }
        }
        query += ");";
        try {
            PreparedStatement ps = conn.prepareStatement(query);
            ps.executeUpdate();
            System.out.println("Data inserted successfully!");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 查询数据
    public static void queryData(String tableName) {
        String query = "SELECT * FROM " + tableName + ";";
        try {
            PreparedStatement ps = conn.prepareStatement(query);
            ResultSet rs = ps.executeQuery();
            while (rs.next()) {
                System.out.println(rs.getString(1) + " " + rs.getString(2) + " " + rs.getString(3));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 更新数据
    public static void updateData(String tableName, String[] data, String condition) {
        String query = "UPDATE " + tableName + " SET ";
        for (int i = 0; i < data.length; i++) {
            query += data[i].split("=")[0] + "='" + data[i].split("=")[1] + "'";
            if (i != data.length - 1) {
                query += ",";
            }
        }
        query += " WHERE " + condition + ";";
        try {
            PreparedStatement ps = conn.prepareStatement(query);
            ps.executeUpdate();
            System.out.println("Data updated successfully!");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 删除数据
    public static void deleteData(String tableName, String condition) {
        String query = "DELETE FROM " + tableName + " WHERE " + condition + ";";
        try {
            PreparedStatement ps = conn.prepareStatement(query);
            ps.executeUpdate();
            System.out.println("Data deleted successfully!");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

3. Main.java - 用于测试数据库管理系统的类

public class Main {

    public static void main(String[] args) {
        // 连接数据库
        Connection conn = DBConnect.connect();
        // 插入数据
        String[] data1 = {"001", "John", "Doe"};
        DBManager.insertData("employee", data1);
        // 查询数据
        DBManager.queryData("employee");
        // 更新数据
        String[] data2 = {"name=Jane", "surname=Doe"};
        DBManager.updateData("employee", data2, "id='001'");
        // 查询数据
        DBManager.queryData("employee");
        // 删除数据
        DBManager.deleteData("employee", "id='001'");
        // 查询数据
        DBManager.queryData("employee");
        // 关闭连接
        try {
            conn.close();
            System.out.println("Connection closed successfully!");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

以上是一个简单的数据库管理系统的代码示例，你可以根据自己的需求进行修改和扩展。