请教个Java内存泄露问题

我最近编程时 碰到了Java内存泄露问题，那位大哥能帮帮我  如何避免这个问题
import java.util.*;
import java.sql.*;
public class OutputArticle{
Set <Article> articles = new HashSet <Article>();
public OutputArticle(){
    Connection conn = DB.getConn();
    tree(articles,conn,0);
    for(Iterator <Article> it = articles.iterator();it.hasNext();){
                Article b = it.next();
                System.out.println(b.getTitle());
            }
    DB.close(conn);
  }
  public static void main(String[] args){
  new OutputArticle();
  }
private void tree(Set <Article> articles,Connection conn,int id){
String sql = "select * from article where pid="+id;
Statement stmt = DB.getStmt(conn);
ResultSet rs = DB.getResultSet(stmt,sql);
try{
while(rs.next()){
Article a = new Article();
a.setId(rs.getInt("id"));
a.setPid(rs.getInt("pid"));
a.setRootid(rs.getInt("rootid"));
a.setTitle(rs.getString("title"));
a.setPdate(rs.getTimestamp("pdate"));
a.setIsleaf(rs.getInt("isleaf&