SetRGB Has No Effect On Alpha Bits

I am using something a kin to this:

for (int w=0;w<bi.getWidth();w++) {
for (int h=0;h<bi.getHeight();h++) {
int color = bi.getRGB(w, h);
color = color << 5;
bi.setRGB(w, h, color);
}
}

I am using a solid green image so

11111111000000001111111100000000

I just wanted to see how it looked so bumped it over 5 places (obviously changing the color). To my surprise, there was no added transparency. I mean moving it to the left would make the alpha:

11100000

I am thinking that setRGB() doesn't effect alpha. Is this accurate?Tested it and in fact setRGB has no effect on the alpha bits. So now the question is how can I gain access to them. I am going to look into the writable Raster API. Perhaps, I can also use a modified awt to access directly OS data.