I know this is simple thing, but i was not aware.
I used println in gsp file and expected to print output in console. But this is showing on page.
<%
for(int i =0; i < threads.size();i++) {
println i
}
%>
thanks.
You can use
<%
System.out.println i
%>
But why use sniplets in a GSP page?
If you want console debug output from your GSP i suggest using this plugin: https://grails.org/plugin/debug