如何将Java long值保存到文件？

So iv'e been trying to find a way of saving a "long" value to a file. I'm using the Twitter4j packages. When I get a list of Followers IDs, it saves them into a long variable. I can do a System Out Print of the value, but I can't write it to a file. I'll show it in the code.So iv'e been trying to find a way of saving a "