The string.format() method listed in the Apex Documentation does not work.

This (and every other combinations I tried) generate a compile error 'method does not exist or wrong signature' !

<code> 

    double subTotal = 1000.0;
   

    strind s = string.format('{0,number,currency}', subTotal);

</code> 

Is there a way to do such a basic formating using APEX ?!?

Thanks,