JSP scripting questions

I'm studying SWCD by Charles Lyons (2nd edition) and i'm reviewing some questions about JSP. On page 262, here's the following question:

Which of the following ca开发者_Python百科use the value 'yes' to be written to the response if the state scripting variable is true and 'no' otherwise?

A. <%= if (state) { "yes"; } else { "false"; } %>

B. <%=state? "yes" : "no"%>

C. <% if (state) %>yes<%else%>no

D. <% if (state) out.write("yes"); else out.write("no");%>

E. <% state? out.write("yes") : out.write("no");%>

Answer is B & D. I do understand the explanation to the answer given. However nothing is mention about why A is incorrect? I don't see why A is incorrect. Any help is appreciated.

This is the difference between the expression ( <%= expressions %> ) and scriptlets ( <% code %>) .

For the expression ,anything inside <%= %> will be get evaluated to a string and this string is inserted into the servlet's output stream directly when the JSP is converted to the servlet. So <%= expressions %> will convert to out.println(expressions). There should be no semicolon at the end of the expression , because out.println(expressions;) has the syntax error after the JSP is converted to the servlet.

For the scriptlets , anything inside <% %> will directly inserted as raw Java code in the service method of the generated Servlet. So <% code(); %> will convert to code();

So , for the option A , <%= if (state) { "yes"; } else { "false"; } %> will convert to the out.println(if (state) { "yes"; } else { "false"; } ) , which have syntax error .So A is incorrect