code: private static long getSizeOfPhysicalMemory() {
  		switch (OperatingSystem.getCurrentOperatingSystem()) {
  			case LINUX:
  				return getSizeOfPhysicalMemoryForLinux();
  				
  			case WINDOWS:
  				return getSizeOfPhysicalMemoryForWindows();
  				
  			case MAC_OS:
  				return getSizeOfPhysicalMemoryForMac();
  				
  			case FREE_BSD:
  				return getSizeOfPhysicalMemoryForFreeBSD();
  				
  			case UNKNOWN:
  				LOG.error("Cannot determine size of physical memory for unknown operating system");
  				return -1;
  				
  			default:
  				LOG.error("Unrecognized OS");
  				return -1;
  		}
  	}
docs: Returns the size of the physical memory in bytes.
  
  @return the size of the physical memory in bytes or <code>-1</code> if
  the size could not be determined