behind the scenes { Question from JWhiz }

[ersin eser]

Question says is following going to compile?
<%! int i ; %>
<% if (i==0)%>
<% i++; %>
<% else %>
<%= "i==1" %>
I said yes, thinking one line statements does NOT need braces
They say No won't compile because missing braces. Well I don't buy that I tried it and did not compiled saying else without if . No ! Why ? What do you think ?
Ok then go to work directory and see the code when no braces
out.write("\r\n");

if (i==0)
out.write("\r\n");
i++;
out.write("\r\n");
else
out.write("\r\n");
out.print( "i==1" );

Heh he not the braces the line brakes messes you up !! Thus you need braces, but where ?
How about this :
<%! int i ; %>
<% if (i==0)%>
<% {i++;} %>
<% else { %>
<%= "i==1" }%>
What do you think ?
No ! this is what you end up having in _jspService
out.write("\r\n");
if (i==0)
out.write("\r\n");
{i++;}
out.write("\r\n");
else {
out.write("\r\n");
out.print( "i==1" });
Heh he not what you expected !
Torture continues
<%! int i ; %>
<% if (i==0) {%>
<% i++;} %>
<% else { %>
<%= "i==1" %>
<% }%>
What do you think ?
No Again !
out.write("\r\n");
if (i==0){
out.write("\r\n");
i++;}
out.write("\r\n");
else {
out.write("\r\n");
out.print( "i==1" });
Did you see that out.write that is the one messes your if structure.
Now I still say that the explanation of the answer was not proper missing thing is not the { and } the placement of them is important.
And I still insist that you don't need the braces
Here you go !
<%! int i ; %>
<%if(i==0)%><% i++; %><% else %><%= "i==1" %>
What do you think ?
Of course it works Here what you get after compilation:

out.write("\r\n");
if(i==0)
i++;
else
out.print( "i==1" );
Of course in all cases i is being declared as instance variable: int i ;
Watch those damn line breaks \r\n
[ February 01, 2002: Message edited by: ersin eser ]

[Madhav Lakkapragada]

one ersin. Really good one.
Thanks.
Actually, without realising this
fact I always used code like this
in my JSPs:
<%! int i ; %>
<% if (i==0) {%>
<% i++;%>
<% }else { %>
<%= "i==1" %>
<% }%>
You see the closing brace of the if stmt goes
just before the else keyword. And the else keyword is immediately followed by the opening brace.
regds.
- satya

[Jim Bertorelli]

The key to solving such questions is to visualize the given code in the servlet form. This will immediately tell you whether it'll compile or not.

[Madhav Lakkapragada]

in the servlet form
yea....acc to what app server. Don't you think this is app server dependent. Well I now know how Tomcat does it... :roll:
- satya....can't stand the pressure of learning more!!!