Apex Method of the Day – Method (and other) Declarations in Anonymous Blocks

An anonymous block is Apex code that does not get stored in the metadata, but that can be compiled and executed using… Developer Console, Force.com IDE [or] The executeAnonymousSOAP API call

A method can be defined and called within an Anonymous Block:

Decimal d1 = 123;
Decimal d2 = 456;
system.debug(multiply(d1,d2));

Decimal multiply(Decimal val1, Decimal val2)
{
   return val1 * val2;
}

An exception can be defined and thrown within an Anonymous Block:

if(true) throw new AnonymousException('Foo!');
system.debug('We will not reach here');

class AnonymousException extends Exception {}

A class can be defined and instantiated within an Anonymous Block:

Mean m = new Mean();

for(Account item : [select AnnualRevenue from Account where AnnualRevenue<>null limit 100])
   m.add(item.AnnualRevenue);

system.debug(m.get());

class Mean
{
   Decimal total = 0;
   Decimal count = 0;

   void add(Decimal value)
   {
      total+=value;
      count++;
   }

   Decimal get()
   {
      return total/count;
   }
}

Force.com Apex Code Developer’s Guide – Anonymous Blocks