I just discovered that, counter-intuitive though it may seem, the fastest way to "format" a blank string to a 0 while keeping all boolean values the same is to double-negate it. It's also by far the most consistent, time-wise.
All tests were run 1000000 times using getRealTime() to measure the time taken.
!!1 - 951 MS total (0.000951 MS per check)
!!0 - 952 MS total (0.000952 MS per check)
!!"" - 920 MS total (0.000920 MS per check)
1+0 - 4992 MS total (0.004992 MS per check)
0+0 - 1419 MS total (0.001419 MS per check)
""+0 - 1392 MS total (0.001392 MS per check)
1*1 - 5148 MS total (0.005148 MS per check)
0*1 - 1436 MS total (0.001436 MS per check)
""*1 - 1400 MS total (0.001400 MS per check)
Well then, I'll have to remember that.