jsp的小问题，头晕了！！！

<%@ page pageEncoding="GBK"%>
<%@ page import="java.sql.*, com.jun.bbs.*, java.util.*, java.io.*"%>

<%!
private void tree(Set <Article> articles, Connection conn, int id, int grade) {
  String sql = "select * from article where pid = " + id;
  Statement stmt = DB.getStmt(conn);
  ResultSet rs = DB.executeQuery(stmt, sql);
  try{
  while(rs.next()) {
  Article article = new Article();
  article.setId(rs.getInt("id"));
  article.setPid(rs.getInt("pid"));
  article.setRootid(rs.getInt("rootid"));
  article.setTitle(rs.getString("title"));
  article.setLeaf(rs.getInt("leaf") == 0? true:false);
  }
  } catch(SQLExpection e) {
  e.printStackTrace();
}
}
%>

<%
List <Article> articles = new ArrayList <Article>();
Connection conn = DB.getConn();
tree(articles, conn, 0, 0);
DB.close(conn);
%>

写了一半遇到错了，找了半天没找到，各位帮忙看下，在new List是报错，说List不是个类，catch那也报错。。。

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lg

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List 和 Set 不是一个体系的，不能转换。
改改
private void tree(Collection <Article> articles, Connection conn, int id, int grade)
{{