@Named
public class NumberHolder {
    private double number = 3.1456780;
    //getters and setters
}

<h:outputText value="#{numberHolder.number}">
    <f:convertNumber type="currency"/>
</h:outputText>

¤3.15

<h:outputText value="#{numberHolder.dbl}">
    <f:convertNumber type="currency" currencyCode="MXN" />
</h:outputText>

MXN3.15

<h:outputText value="#{numberHolder.dbl}">
    <f:convertNumber type="currency" maxFractionDigits="3" />
</h:outputText>

¤3.146

<h:outputText value="#{numberHolder.dbl}">
    <f:convertNumber pattern="£###,###,##0.000" />
</h:outputText>

£3.146

<h:outputText value="#{numberHolder.dbl}">
    <f:convertNumber pattern="£###,###,##0.000" maxFractionDigits="2" />
</h:outputText>

£3.15

<h:outputText value="#{numberHolder.dbl}">
    <f:convertNumber pattern="£###,###,##0.00" currencySymbol="$" />
</h:outputText>

£3.15

<h:outputText value="#{numberHolder.dbl}">
    <f:convertNumber pattern="###,###,##0.00" currencySymbol="$" />
</h:outputText>

3.15

<h:outputText value="#{numberHolder.dbl}">
    <f:convertNumber pattern="###,###,##0.00" type="currency" currencySymbol="$" />
</h:outputText>

3.15