Comments on: Implementing a simple cache with Java http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/ Writing about my experiences with technology and all different kinds of projects and experiments Mon, 30 Jan 2012 19:10:22 +0000 hourly 1 By: Christian Schenk http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/comment-page-1/#comment-49401 Christian Schenk Thu, 22 Dec 2011 07:14:23 +0000 http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/#comment-49401 Hi Kamel, if you're using a synchronized map you don't have to encapsulate it inside a synchronized block; the same holds true for a synchronized HashTable, which is just a certain implementation of a map. If you checkout the code in the comment above in more detail you'll notice that two objects are altered inside the synchronized block. That said, the synchronized block makes sure that changing both objects is a single atomic operation. Hi Kamel,
if you’re using a synchronized map you don’t have to encapsulate it inside a synchronized block; the same holds true for a synchronized HashTable, which is just a certain implementation of a map.
If you checkout the code in the comment above in more detail you’ll notice that two objects are altered inside the synchronized block. That said, the synchronized block makes sure that changing both objects is a single atomic operation.

]]> By: Kamel http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/comment-page-1/#comment-48925 Kamel Mon, 19 Dec 2011 10:56:49 +0000 http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/#comment-48925 Hi Christian, Thanks so much about your code, I have noticed in comments we sill need to but synchronize block around maps when tries to remove. Can you please explain to me why I need that point as I can see you already creating synchronized map. or what if you used hashtable instead. Thanks Hi Christian,
Thanks so much about your code, I have noticed in comments we sill need to but synchronize block around maps when tries to remove. Can you please explain to me why I need that point as I can see you already creating synchronized map. or what if you used hashtable instead. Thanks

]]> By: Christian Schenk http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/comment-page-1/#comment-48189 Christian Schenk Thu, 15 Dec 2011 15:14:25 +0000 http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/#comment-48189 Dear Indrajit, I'm glad this post helped you. Don't forget to checkout the <a href="http://data.christianschenk.org/implementing-a-simple-cache-with-java/xref/index.html" rel="nofollow">source code</a> and play with it a bit - this way you'll probably understand the concepts even better. Dear Indrajit,
I’m glad this post helped you. Don’t forget to checkout the source code and play with it a bit – this way you’ll probably understand the concepts even better.

]]> By: Indrajit Yadav http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/comment-page-1/#comment-48177 Indrajit Yadav Thu, 15 Dec 2011 14:14:21 +0000 http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/#comment-48177 Hi All, I am new for caching concept but after reading simple caching in java, and all your's comments i am happy it is giving more information to understand this concept and proceed further. Thanks ! Hi All,

I am new for caching concept but after reading simple caching in java, and all your’s comments i am happy it is giving more information to understand this concept and proceed further.

Thanks !

]]> By: Brajendra N Mishra http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/comment-page-1/#comment-33287 Brajendra N Mishra Tue, 07 Jun 2011 12:48:17 +0000 http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/#comment-33287 Thanks a Lot Christian, I got what I needed. It is described in very simple and precise manner. I like it. It would help me out in my exisiting project. Thanks a Lot Christian,
I got what I needed.
It is described in very simple and precise manner. I like it. It would help me out in my exisiting project.

]]> By: Christian Schenk http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/comment-page-1/#comment-32763 Christian Schenk Thu, 26 May 2011 07:50:27 +0000 http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/#comment-32763 Hi Maldalapu, sure, that's one way to do it. You only need one synchronized block and won't have to add <code>synchronized</code> to every method. Hi Maldalapu,
sure, that’s one way to do it. You only need one synchronized block and won’t have to add synchronized to every method.

]]> By: Maldalapu http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/comment-page-1/#comment-32721 Maldalapu Wed, 25 May 2011 11:26:10 +0000 http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/#comment-32721 Here is what I have done: <pre lang="java"> private void createRemoveRunnable(final K name) { synchronized (this) { cacheStore.remove(name); expire.remove(name); } } </pre> And is it required to keep synchronized block in <code>removeExpired()</code> method ? If yes please let me know how do I do that ? Here is what I have done:

private void createRemoveRunnable(final K name) {
  synchronized (this) {
    cacheStore.remove(name);
    expire.remove(name);
  }
}

And is it required to keep synchronized block in removeExpired() method ? If yes please let me know how do I do that ?

]]> By: Christian Schenk http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/comment-page-1/#comment-32694 Christian Schenk Tue, 24 May 2011 21:03:35 +0000 http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/#comment-32694 Hi Maldalapu, sure you can do this. Remember encapsulating these two operations in a <code>synchronized</code> block, like it was mentioned earlier in the comments. Hi Maldalapu,
sure you can do this. Remember encapsulating these two operations in a synchronized block, like it was mentioned earlier in the comments.

]]> By: Maldalapu http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/comment-page-1/#comment-32675 Maldalapu Tue, 24 May 2011 16:25:29 +0000 http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/#comment-32675 Is it required to have a separate thread to remove entries from cache ? Like below <pre lang="java"> public void run() { cacheStore.remove(name); expire.remove(name); } </pre> Can't we keep the same inside after <code>threads.execute(createRemoveRunnable(name));</code> in <code>removeExpired()</code> method ? Is it required to have a separate thread to remove entries from cache ? Like below

public void run() {
  cacheStore.remove(name);
  expire.remove(name);
}

Can’t we keep the same inside after threads.execute(createRemoveRunnable(name)); in removeExpired() method ?

]]> By: Christian Schenk http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/comment-page-1/#comment-30259 Christian Schenk Tue, 19 Apr 2011 08:33:07 +0000 http://www.christianschenk.org/blog/implementing-a-simple-cache-with-java/#comment-30259 Hi Rohit, as the name implies <code>SimpleCache</code> is a really simple solution to cache objects of a certain type. It isn't very sophisticated but may serve as a foundation for a more intelligent implementation. In your case with lots and lots of records I could think of the following solutions: <ol> <li>limit the amount of cached objects and throw away the oldest objects on expiry not making any use of expiry after a certain amount of time.</li> <li>split the cache into various smaller segments that can be handled in a reasonable amount of time. Right now the implementation has got a map of objects and you could extend that to a map containing maps of objects. During the expiry run only work on a subset of these maps in the larger map.</li> </ol> Both solutions may help you limiting the set you will have to work on during an expiry run. Hi Rohit,
as the name implies SimpleCache is a really simple solution to cache objects of a certain type. It isn’t very sophisticated but may serve as a foundation for a more intelligent implementation.
In your case with lots and lots of records I could think of the following solutions:

  1. limit the amount of cached objects and throw away the oldest objects on expiry not making any use of expiry after a certain amount of time.
  2. split the cache into various smaller segments that can be handled in a reasonable amount of time. Right now the implementation has got a map of objects and you could extend that to a map containing maps of objects. During the expiry run only work on a subset of these maps in the larger map.

Both solutions may help you limiting the set you will have to work on during an expiry run.

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