写一个Jdbc程序，使用Druid包实现增删改查功能，正确回收连接

要编写一个使用Druid包的JDBC程序来实现增删改查操作并确保正确回收连接，首先你需要添加Druid依赖，并设置其配置。以下是一个简单的示例：

import com.alibaba.druid.pool.DruidDataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class DruidJdbcExample {

    private static final String DB_URL = "jdbc:mysql://localhost:3306/test";
    private static final String USER = "username";
    private static final String PASS = "password";

    // 创建DruidDataSource实例
    private static final DruidDataSource dataSource = new DruidDataSource();
    static {
        dataSource.setUrl(DB_URL);
        dataSource.setUsername(USER);
        dataSource.setPassword(PASS);
        dataSource.init();  // 初始化数据源
    }

    public void CRUDOperations() {
        Connection conn = null;
        PreparedStatement pstmt = null;

        try {
            // 获取连接
            conn = dataSource.getConnection();

            // 插入操作
            String insertSql = "INSERT INTO table_name (column1, column2) VALUES (?, ?)";
            pstmt = conn.prepareStatement(insertSql);
            pstmt.setString(1, "value1");
            pstmt.setString(2, "value2");
            pstmt.executeUpdate();

            // 查询操作
            String selectSql = "SELECT * FROM table_name WHERE column1 = ?";
            pstmt = conn.prepareStatement(selectSql);
            pstmt.setString(1, "value1");
            ResultSet rs = pstmt.executeQuery();
            while (rs.next()) {
                System.out.println(rs.getString("column1"));
            }

            // 更新操作
            String updateSql = "UPDATE table_name SET column1 = ? WHERE id = ?";
            pstmt = conn.prepareStatement(updateSql);
            pstmt.setString(1, "new_value");
            pstmt.setInt(2, 1);
            pstmt.executeUpdate();

            // 删除操作
            String deleteSql = "DELETE FROM table_name WHERE id = ?";
            pstmt = conn.prepareStatement(deleteSql);
            pstmt.setInt(1, 1);
            pstmt.executeUpdate();

        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 确保关闭资源
            try {
                if (pstmt != null) pstmt.close();
                if (conn != null && !conn.isClosed()) conn.close();
            } catch (SQLException ex) {
                ex.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        new DruidJdbcExample().CRUDOperations();
    }
}

在这个例子中，我们创建了一个`DruidDataSource`实例，然后在每个操作的开始获取连接，在操作结束后确保关闭`PreparedStatement`和`Connection`。使用finally块可以确保资源总是得到正确关闭，即使发生异常也是如此。