I want to convert this decimal value 10600.05 into 10,600 in APEX. and I am trying with this code
 

Decimal rA = 10600.86;
Integer Intval=ra.intvalue();
List<String> args = new String[]{'0','number','###,###,###,###'};
String s = String.format(Intval.format(), args);

But I am always getting 

10 600 as output. Comma is not coming in output. I want this only in APEX and in VF page. Any help please?

I"m trying to create a validation rule when a change to a record is made but the Employment picklist is blank (aka no values have been selected), the user must make a selection in the picklist before saving. I tried this formula but its not working as intended. Any ideas? Thanks
 

AND(
ISCHANGED(Id),
NOT(ISBLANK(TEXT(Employment__c))))