how can I get the number of reducer in Map

[rabbit_cheng]

In my map function, I  need to know the number of reducer, the code segment in 
my program like this:
   JobConf job = new JobConf(driverClass.class);
    int numReducer=job.getNumReduceTasks();
but the function invocation job.getNumReduceTasks() always returns the value of 
"1". I have tested many times: In driver function, I set the number of reducer 
to 2 using the following statements:
    JobConf job =new JobConf(driverClass.class);
    job.setNumReduceTasks(2);
As a result, the reducers' output file number is 2, so I know the  statements 
above worked, but what I get in map function is still to be "1".  How can I get 
the right number of reducer in map function? thanks!