Future

Future was introduced in Java 7. It represents the result of an asynchronous computation that may or may not have completed. One way to think of it is like this:

  Future<Double> futureResult = some_very_slow_calculation( ... );
  // since the some_very_slow_calculation( ... ) method is async, we get the
  // Future<Double> (thus reach here) immediately, usually before the calculation is done.

  /* why wait? I can go work on something else! */
  do_some_other_work();

  // now maybe the slow calculation is done?
  Double result = futureResult.get();  // this is a BLOCKING call

Of course we rarely use Future in the above manner, since it is too wishful thinking. What if do_some_other_work() needs the result of the calculation? What if do_some_other_work() finishes too quickly, and we are back at

  Double result = futureResult.get();

which is blocking?

Fortunately Future also offers get() with timeout, isDone(), and cancel(). One of the more common ways to use Future, is actually to use FutureTask, which implements Future. We could do something like this:

  // private static final ExecutorService THREAD_POOL = Executors.newFixedThreadPool(8);

  FutureTask<Double> ft = new FutureTask<Double>( ()->very_slow_blocking_calculation( ... ) );
  try {
      THREAD_POOL.execute(ft);
      Double result = ft.get(1000, TimeUnit.MILLISECONDS);  // 1 second timeout
      // continue to do other work, with result
      . . .
  } catch (Exception e) {
      e.printStackTrace();
      ft.cancel(true);
  }

Or, if we don’t want to give up so easily (let’s say the very_slow_blocking_calculation is important), we could

  // private static final ExecutorService THREAD_POOL = Executors.newFixedThreadPool(8);

  FutureTask<Double> ft = new FutureTask<Double>( ()->very_slow_blocking_calculation( ... ) );
  try {
      THREAD_POOL.execute(ft);
      while( !ft.isDone() ) {
          // while we wait, we can go work on something else
          do_some_other_work();
      }
      Double result = ft.get();  // this will return immediately
      . . .
  } catch (Exception e) {
      e.printStackTrace();
      ft.cancel(true);
  }

A complete Java source code can be found here.

• Part I (this article): Future explained
• Part II: Future vs Promise
• Part III: Use Promise to combine multiple async requests, serial or parallel

• Get it from github.
• See the live demo.
• See it in action on my own blog.

Welcome to the sample post for the Jekyll Clean theme.

A simple and clean Jekyll theme using bootstrap (not to be confused with jekyll-bootstrap) that’s easy to modify and very modular in component and element reuse.

It uses Disqus for comments and includes Google Analytics support. Both of these features are disabled by default and can be enabled via _config.yml. You can also rip this code out of the templates if you like (footer.html and post.html). The beauty of Jekyll - keep things clean… Jekyll Clean!

The theme works well on mobile phones, using a collapsable nav bar and hiding the sidebar. The links pane in the sidebar is available on mobile through the nav menu, and you can do the same thing for any other sections added to the sidebar.

Don’t forget to occassionally merge against my upstream repository so you can get the latest changes. Pull requests are encouraged and accepted!

Installation

If you don’t have a blog already on github, start by cloning this repository. Best to do that directly on github and then clone that down to your computer.

If you already do have a blog, You can certainly apply this theme to your existing blog in place, but then you won’t be able to merge as the theme changes. If you re-apply your blog history on top of this theme’s gh-pages branch, it’s then easy to update to the latest version of the theme. You also don’t want to have to deal with resolving old conflicts from your existing history, so you may wish to to push your existing master off to a new branch so you have the old history and start a new branch with this as the start, merging in your _posts and other assets (after git rm’ing the current _posts.

Not ideal, but you have to make a choice - either apply it manually or base your blog off this theme’s branch. Either way it will work, and both have their own pros and cons.

You can setup an upstream tracking repository like so:

$ git remote add upstream git@github.com:scotte/jekyll-clean.git

And now when you wish to merge your own branch onto the latest version of the theme, simply do:

$ git fetch upstream
$ git merge upstream/gh-pages

Of course you will have to resolve conflicts for _config.yml, _includes/links-list.html, and _posts, and so on, but in practice this is pretty simple.

This is how I maintain my own blog which is based on this theme. The old history is sitting in an old-master branch that I can refer to when I need to.

Running Locally

Here’s the exact set of packages I need to install on Debian to run jekyll locally with this theme for testing.

$ sudo aptitude install ruby ruby-dev rubygems nodejs
$ sudo gem install jekyll jekyll-paginate

And then it’s just a simple matter of running jekyll locally:

$ jekyll serve --baseurl=''

Now browse to http://127.0.0.1:4000

Using gh-pages

Running a jekyll site is a bit outside the scope of this doc, but sometimes it can be a bit confusing how to configure jekyll for project pages versus user pages, for example.

To start with, read through the documentation here. This will provide a good overview on how it all works. The git branch and baseurl (in _config.yml) will change depending on the sort of site deployed.

When you clone this repository, it’s set up for project pages, so the deployed branch is “gh-pages” and baseurl is configured to ‘jekyll-clean’, because that’s the name of this project.

If you plan to deploy this as user pages (like I do for my own blog), the deployed branch is “master” and baseurl is configured to ‘’ (i.e. empty).

Comment Systems

Jekyll clean supports both isso and disqus comment systems.

After enabling comments, either isso or disquss must be configured. Don’t try configuring both!

Isso Comments

Isso requires running a local server, so is not suitable for hosting in github pages, for example. Isso is open source and keeps all your data local, unlike Disqus (who knows exactly what they are doing with your data).

In _config.yml you’ll need to set isso to the fully-qualified URL if your isso server (this is the value for data-isso passed to the isso JS). Make sure comments is true.

Disqus Comments

Getting Disqus to work can be a bit more work than it seems like it should be. Make sure your Disqus account is correctly configured with the right domain of your blog and you know your Disqus shortname.

In _config.yml you’ll need to set disqus to your Disqus shortname and make sure comments is true.

Finally, in posts, make sure you have comments: true in the YAML front matter.

More information on using Disqus with Jekyll is documented here.

Code Syntax Highlighting

To use code syntax highlighting, use the following syntax:

```python
import random

# Roll the die
roll = random.randint(1, 20)
print('You rolled a %d.' % roll)
``` #REMOVE

(Remove #REMOVE from the end of the last line). Which will look like this in the rendered jekyll output using the default css/syntax.css provided with this theme (which is the colorful theme from https://github.com/iwootten/jekyll-syntax):

import random

# Roll the die
roll = random.randint(1, 20)
print('You rolled a %d.' % roll)

You can, of course, use any theme you wish, see the jekyll and pygments documentation for more details.

License

The content of this theme is distributed and licensed under a Creative Commons Attribution 4.0 License

This license lets others distribute, remix, tweak, and build upon your work,
even commercially, as long as they credit you for the original creation. This
is the most accommodating of licenses offered. Recommended for maximum
dissemination and use of licensed materials.

In other words: you can do anything you want with this theme on any site, just please provide a link to the original theme on github so I get credit for the original design. Beyond that, have at it!

This theme includes the following files which are the properties of their respective owners:

• js/bootstrap.min.js - bootstrap
• css/bootstrap.min.css - bootstrap
• js/jquery.min.js - jquery
• images/cc_by_88x31.png - creative commons
• css/colorful.css - iwootten/jekyll-syntax