When comparing Eclipse vs IntelliJ IDEA, the Slant community recommends IntelliJ IDEA for most people. In the question“What are the best Java IDEs?” IntelliJ IDEA is ranked 1st while Eclipse is ranked 5th. The most important reason people chose IntelliJ IDEA is:
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.
Ranked in these QuestionsQuestion Ranking
Pro Fast compiler
Eclipse uses a custom compiler (which can also be used outside of Eclipse), which is often faster than the normal Java Compiler, especially for incremental compilation.
Pro Large selection of plugins
Eclipse has a large and active community, which has resulted in a wide variety of plugins.
Pro Highly customizable
Thanks to the large variety of plugins and various configuration options, Eclipse is very customizable.
Pro Free and open source
Eclipse is an open source project and free to use.
Pro Good font rendering
Because Eclipse is based on SWT, it uses the native font rendering and thus looks better than other IDEs on some Linux systems, where the Java font rendering is not optimal.
Pro Multiple languages - one IDE
Pro Good refactoring tools
Pro Great debugger
Shows threads, concurrency locks, and conditional breakpoints.
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 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 Android support, JavaEE support, etc
A very complete development environment support.
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 Support for many languages
IntelliJ supports many languages besides Java, some of these are: golang, Scala, Clojure, Groovy, Bash, etc...
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 Clear and detailed documentation
The documentation is exhaustive, easy to navigate, and clearly worded.
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.
Con UI can be confusing
There's an overly abundant presence of menus, this forces you to constantly click around the different menu structures; foreign ideas, like Views and Perspectives; strange menu choices, like configure settings located in Windows menu->Preferences.
Con Lack of plugins with good user interfaces
Many Eclipse plugins are extremely confusing, with UIs that are even less consistent than Eclipse itself.
Con Plugins can be unstable
Though there are plenty of plugins to choose from, they aren't always reliable. Some aren't maintained, bug fixes can be slow, and you may need to download plugins from multiple sources.
Con Poor language support via plugins
Eclipse supports other languages with a huge amount of plugins. Many languages have their own distribution, but multi-language is hard to exist in one project. Like Scala, there is no official support from Eclipse for this language. If Eclipse gets an update, languages such as these will not.
Con Some old bugs don't get fixed
E.g. change a parameter name to the same as a field - the field will not be prefixed with "this." like in IDEA.
Con Tends to be slow and lags a lot
Con Newer versions are getting less stable
Eclipse 4 Neon randomly hangs. For example, during installing new software.
Con Built with closed source components
The version with full features is not opensource. Parts of the code are under apache licence though.
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 Slow startup
Con Uses too much RAM
Con Lack of plugins
IntelliJ supports a very small amount of plugins. Althrough thesse are 'quality approved', many features are missing and can't be implemented because of that.
Con Cannot open multiple projects in the same window
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).