Hi there!!!
I am new here and new student.

I got a question here.

If I want to detect whether there is an illegal charater(inside red) - other than what is provided now. how do i have to do it? Thanks in advance.

<html>
<body>
<%
for (int i=0;i<5;i++)
{
out.println(i);
}
%>
</body>
</html>

First of all, explain better your problem. What do you mean ?
an illegal charater(inside red) - other than what is provided now

Also the code you posted makes no sense. How is it connected with what you ask. Not to mention that this is how it should be written:

<html>
<body>
<%
for (int i=0;i<5;i++)
{
<%=i%><br/>
}
%>
</body>
</html>
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