Japan doesn't have immigration because it is very hard to get their. Also it isn't in the EU, didn't have a colonial Empire and doesn't need population for its defence. The thing you have to look at with Japan isn't its immigration numbers, but its emigration numbers. Very few Japanese people leave Japan, so they don't need to import people to replace them. Millions of Europeans have left and leave Europe every year, they need to be replaced. I mean 300,000 people left Britain last year, so 300,000 immigrants were need to replace them.
I think I have already made a thread about this, but nobody has taken on board what I said. The turnover of population is the important thing politically, not the numbers of immigrants.