String sqlstring="SELECT username,password FROM Article";
sqlstring+="";
sqlstring+="WHERE username LIKE '"+username+"'";
改为:String sqlstring="SELECT username,password FROM Article";
sqlstring+=" "; //空格没有加
sqlstring+="WHERE username LIKE '"+username+"'";
sqlstring+="";
sqlstring+="WHERE username LIKE '"+username+"'";
改为:String sqlstring="SELECT username,password FROM Article";
sqlstring+=" "; //空格没有加
sqlstring+="WHERE username LIKE '"+username+"'";
String sqlstring="SELECT username,password FROM Article WHERE username LIKE '"+username+"'";
像你这样处理SQL语句很容易出错的