Java Network Programming, Second Edition

Synchronization

My shelves are overflowing with books, including many duplicate books, out-of-date books, and books I haven’t looked at for ten years and probably never will again. Over the years, these books have cost me tens of thousands of dollars, maybe more, to acquire. By contrast, two blocks down the street from my apartment, you’ll find the Central Brooklyn Public Library. Its shelves are also overflowing with books, and over its 150 years, it’s spent millions on its collection. But the difference is that its books are shared among all the residents of Brooklyn, and consequently the books have very high turnover. Most books in the collection are used several times a year. Although the public library spends a lot more on buying and storing books than I do, the cost per page read is much lower at the library than for my personal shelves. That’s the advantage of a shared resource.

Of course, there are disadvantages to shared resources too. If I need a book from the library, I have to walk over there. I have to find the book I’m looking for on the shelves. I have to stand in line to check the book out, or else I have to use it right there in the library rather than bringing it home with me. Sometimes, somebody else has checked the book out, and I have to fill out a reservation slip requesting that the book be saved for me when it’s returned. And I can’t write notes in the margins, highlight paragraphs, or tear pages out to paste on my bulletin board. (Well, I can, but if I ...