IDEA places an emphasis in safe refactoring, offering a [variety of features](https://www.jetbrains.com/idea/features/refactoring.html) to make this possible for a variety of languages. These features include safe delete, type migration and replacing method code duplicates.
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Pro Combines the best parts of Vi and Emacs
Spacemacs combines the Emacs platform (with the full power of the Emacs plugin ecosystem) and the Vi keybindings (via EViL), all in the same box.
Pro Simple but powerful configuration architecture
At the heart of Spacemacs, the configuration layers group packages configuration into semantic units that can be toggled on and off. The architecture is simple but powerful, allowing the user to easily manage configuration dependencies between hundreds of packages.
Pro Above average documentation quality
Documentation is mandatory for each new configuration layer and can be accessed directly within the editor in Org format.
Pro Community-driven configuration
Spacemacs is the biggest community-driven Emacs starter-kit.
Pro Great support from the community
The community surrounding Spacemacs is very active and there is a welcoming gitter chat for users to ask questions.
Emacs runs on Gnu/Linux, Mac OS X, and Windows.
Pro Completely configured out of the box
Stuff like version control, file management, good default theme are all configured out of the box.
Pro Mnemonic and consistent keybindings
Space-lead key bindings are organized in mnemonic namespaces. For instance, buffer actions are under
SPC b, file actions are under
SPC f, project actions are under
SPC p, search actions are under
SPC s, and so on. Keybindings are consistent across the whole distribution thanks to a set of conventions.
Pro Lowers the risk of RSI by using the spacebar as leader
Spacemacs got its name from the fact that it is uses the space bar as a default leader key. The key was chosen because it is easy to press and to hopefully lower the risk of RSI.
Pro Fast-paced development
New functionalities and fixes are added to Spacemacs every day, while release cycles are short.
Pro Gradual learning curve
Evil package is a first class citizen and Spacemacs embraces it from day one. Evil package allows Vim users to be productive very quickly while still allowing regular Emacs users to use Spacemacs.
Pro Can be controlled fully with the keyboard
There's no need to reach for the mouse again since Spacemacs can be fully controlled with keyboard.
Pro Remote file editing
Files can be edited in Spacemacs remotely.
Pro Manage many code bases easily
Pro Offers a number of practical features
Spacemacs has some great features for taking notes, tracking to-do lists, and tracking time.
Pro Great note-taking and agenda "app" built-in
Allows for great organization applications that can be saved in future-proof format, plain text, can be integrated with LaTeX, markdown, HTML, Literate Programming and be committed to source control.
Pro LaTeX support
LaTeX allows for auto-completion, syncing, and more.
Pro Works well with Common Lisp
Pro Can work in terminal mode
Sometimes you only have terminal access, over ssh or something.
Pro Daemon support
Has great daemon support, which can mitigate the issue of slow startup.
Pro Manage R files easily
Pro Great CFEngine support
Syntax highlighting and org-babel extensions.
Pro Easily extended with community plugins
Pro Great Clojure support
Pro Smart refactorings
IDEA places an emphasis in safe refactoring, offering a variety of features to make this possible for a variety of languages.
These features include safe delete, type migration and replacing method code duplicates.
Pro Fast and smart contextual assistance
Uses a fast indexing technique to provide contextual hints (auto-completion, available object members, import suggestions).
On-the-fly code analysis to detect errors and propose refactorization.
Pro Android support, JavaEE support, etc
A very complete development environment support.
Pro Support for many languages
IntelliJ supports many languages besides Java, some of these are: golang, Scala, Clojure, Groovy, Bash, etc.
Pro Clear and detailed documentation
The documentation is exhaustive, easy to navigate, and clearly worded.
Pro Stable and robust
IntelliJ IDEA hardly ever crashes or has any issues that plague other Java IDEs like file corruption or slowness.
Pro Intuitive and slick UI
IDEA has a clean, intuitive interface with some customization available (such as the Darcula theme).
Pro Lots of plugins
Many plugins are available for almost any task a developer may need to cover. Plugins are developed by Jetbrains themselves or by 3rd parties through the SDK available for writing them.
Pro Free version available
There is a free community edition (open source) and an ultimate edition, which you can compare here.
The ultimate edition is available for free for one year for students but must be registered through an .edu e-mail account.
Pro Very powerful debugger
With ability to step into a certain part of a large method invocation (Shift+F7), drop frame, executing code snippets, showing method return values, etc.
Pro Many convenient features
These simplify the daily work, e.g. copy/cut a whole line without the need to select it.
Pro Gradle support
Pro Buit-in Git support
Con Can be quite glitchy at times
Spacemacs combines many packages from many different authors that were never designed to work together. Sometimes they interact in unexpected ways, and things randomly break as one package interferes with another's features. This combined with delayed auto-loading of packages in unpredictable order, different modes for different file types, frequent package updates, and necessary customization by selection of layers and packages, can make these glitches hard to reproduce. It takes a lot of emacs know-how to fix these problems. Fortunately there is a very active community willing to help with these problems, but it might take a while.
Con Functionality layers of complicated configuration
To configure Spacemacs, settings for Emacs/Evil/Spacemacs may need editing. It's not always clear which need to be changed or how to change settings globally: sometimes hooks are needed, other times Spacemacs provides options.
Con Slow startup time
Although configuration is heavily loaded, the starting time of Spacemacs is usually between two and five seconds. Emacs can be run as a daemon though which reduces the client's startup time to a few milliseconds.
Con High CPU and unresponsive at times
There are occasions when Spacemacs would suddenly consume a LOT of CPU and then other times would become completely unresponsive. This instability took place only 6 months or so ago. Restarting Spacemacs can fix it for a while but perhaps this issue is already fixed in newer versions.
Con Complex learning difficulty
You must be familiar with either Vim or Emacs. In addition, you should be familiar with the unique features of Spacemacs. The Layer concept of replacing Emacs settings is still difficult and abstract compared to modern editors.
Con Uses too much RAM
Con Slow startup
Startup can be slow deepending on system configuration
Con Standard hotkeys behave differently
Seems like hotkeys assignment in Idea has no logical consistency.
Like «F3» is usually next match, «Ctrl+W» - close tab, etc — they map to some different action by default.
There is a good effort in making the IDE friendly for immigrants from other products: there are options to use hotkeys from Eclipse, and even emacs. But these mappings are very incomplete. And help pages do not take this remapping into account, rather mentioning the standard hotkeys.
So, people coming from other IDEs/editors are doomed to using mouse and context menus (which are rather big and complex).
Con Bugs are not solved as often as they should
They are more interested in adding new features or issuing new versions than solving bugs.
Con Cannot open multiple projects in the same window
Con Built with closed source components
The version with full features is not opensource. Parts of the code are under apache licence though.
Con Lack of plugins
IntelliJ supports a very small amount of plugins. Although these are 'quality approved', many features are missing and can't be implemented because of that.