Specific If Else Case in Jsf to control the visibility of jsf components

Specific If Else Case in Jsf to control the visibility of jsf components

i have the following panelGroup in jsf:
<h:panelGroup rendered="#{true}">
<h:outputFormat value="#{txt.text_a}">
<f:param value="#{bean.get_a}" />
</h:outputFormat>
</h:panelGroup>
Now i have an another jsf tag:
<h:outputText value="#{bean.get_b}" />
I need inside the outputFormat tag a kind of if-else case to control, wheter
<h:outputFormat value="#{txt.text_a}">
<f:param value="#{bean.get_a}" />
</h:outputFormat>
or
<h:outputText value="#{bean.get_b}" />
is visible. Inside the java bean class, which called "testBean" i have an
value "visible", which a value, which can represent the the checksum for
the if statement.
Is it possible to create this kind of if Else Statment in JSF?
Thanks for helping me!
Greetz Marwief