Getting "Cant find symbol" error while running through ANT

Hi Ashish/folks,

I have been trying to run my test suite through ANT application with addition of following two lines:

driver.manage().window().maximize();
driver.manage().timeouts().implicitlyWait(30, TimeUnit.SECONDS);

But ANT throws an error "Cant find symbol" for above two lines. Interestingly, when i comment those above two lines then ANT runs the code successfully. Could anyone of you geniuses tell me why this is happening.

Thanks in advance
Ahmed Siddiqui