With all their satellite launches, they certainly have the means to deliver them. Letting China know a few things have been assembled would have a chilling effect on Beijing's ambitions if they get frisky with Japan.
What’s the saying they have? I think it’s, Japan is only a screwdriver away from being a nuclear power!
All one has to do to agree with that statement, is to look at a map of Japan and China. What with China and North Korea having nukes, and the closeness of Tokyo to those nations, I would also bet that Japan has the components ready to go. Especially seeing how crappy Obama is to his allies, I don't think the Japanese government should trust the White House to protect Japan if attacked by China and North Korea. (Our troops would be willing but Obama has the final say, and he would probably take his time while playing golf deciding if he should make a decision.)