the MaskClass provide five method as follow(we set a string as 'systemweb'):

1.(LeftToRight):SwMaskLeftToRight(4) = “Sys******”

2.(RightToLeft):SwMaskRightToLeft(4) = “******web”

3.(Range):SwMaskRange(3,7) = “Sy****web”

4.(Random):SwMaskRandom(3) = “yt****b”

5.(Middle):SwMaskMiddle(1,3) = “S*****web”