Migrating from Eclipse to IntelliJ IDEA

Overview

Switching from Eclipse to IntelliJ IDEA, especially if you've been using Eclipse for a long time, requires understanding some fundamental differences between the two IDEs, including their user interfaces, compilation methods, shortcuts, project configuration and other aspects.

User Interface

No workspace

The first thing you'll notice when launching IntelliJ IDEA is that it has no workspace concept. This means that you can work with only one project at a time. While in Eclipse you normally have a set of projects that may depend on each other, in IntelliJ IDEA you have a single project that consists of a set of modules.

If you have several unrelated projects, you can open them in separate windows.

If you still want to have several unrelated projects opened in one window, as a workaround you can configure them all in IntelliJ IDEA as modules.

IntelliJ IDEA vs Eclipse terminology

The table below compares the terms in Eclipse and IntelliJ IDEA:

No perspectives

The second big surprise when you switch to IntelliJ IDEA is that it has no perspectives.

It means that you don't need to switch between different workspace layouts manually to perform different tasks. The IDE follows your context and brings up the relevant tools automatically.

Tool windows

Just like in Eclipse, in IntelliJ IDEA you also have tool windows. To open a tool window, simply click it in the tool window bar:

If the tool window bar is hidden, you can open any tool window by hovering over the corresponding icon in the bottom left corner:

If you want to make the tool window bar visible for a moment, you can press Alt (Cmd for macOS) twice and hold it.

If you don't want to use the mouse, you can always switch to any toolbar by pressing the shortcut assigned to it. The most important shortcuts to remember are:

• Project: ⌘1⌘1⌥1⌥1
• Version Control: ⌘9⌘9⌘9⌥9⌥9
• Terminal: ⌥F12⌥F12⌥F12⌥F12⌥F12

Another thing about tool windows is that you can drag, pin, unpin, attach and detach them:

To help store/restore the tool windows layout, there are two useful commands:

• Window | Store Current Layout as Default
• Window | Restore Default Layout (also available via ⌘F12⌘F12⌘O⌃F12⌃F12)

Multiple windows

Windows management in IntelliJ IDEA is slightly different from Eclipse. You can't open several windows with one project, but you can detach any number of editor tabs into separate windows.

Auto-scrolling to/from sources

By default, IntelliJ IDEA doesn't change the selection in the Project Tool Window when you switch between editor tabs. However, you can enable it in the tool window settings:

Enabling line numbers

Line numbers are not shown in the editor by default. To enable them, go to Settings/Preferences | Editor | General | Appearance | Show line numbers. There you will also find other useful settings.

General workflows

No 'save' button

Time for some really shocking news: IntelliJ IDEA has no Save button. Since in IntelliJ IDEA you can undo refactorings and revert changes from Local History, it makes no sense to ask you to save your changes every time.

Still, it's worth knowing that physical saving to disk is triggered by certain events, including compilation, closing a file, switching focus out of the IDE, etc. You can change this behavior via Settings | Appearance & Behavior | System Settings:

No save actions

One of the features you may miss in IntelliJ IDEA as an Eclipse user is save actions, i.e. the actions triggered automatically on save, such as reformatting code, organizing imports, adding missing annotations and the final modifier, etc. Instead, IntelliJ IDEA offers you to run the corresponding actions automatically on commit:

Or manually:

• Code | Reformat Code (⌥⌘L⌥⌘L⇧⌘F⌥F8)
• Code | Optimize Imports (⌃⌥O⌥⌘O⇧⌘O⌃⌥O⌃⌥O)
• Analyze | Code Cleanup

If, for some reason, you can't live without an Eclipse save action, you can install a plugin that imitates Eclipse save actions.

Compilation

The way IntelliJ IDEA compiles projects is different from Eclipse in a number of ways.

Auto-compilation

By default, IntelliJ IDEA doesn't automatically compile projects on saving because normally we don't invoke the save action explicitly in IntelliJ IDEA.

If you want to mimic the Eclipse behavior, you can invoke the Make Project action (⌘F9⌘F9⌘BF7⌃F9) - it will save the changed files and compile them. For your convenience, you can even reassign the ⌘S⌘S⌘S⌃S⌃X, ⌃S shortcut to the Make Project action.

To enable automatic compilation, navigate to Settings/Preferences | Build, Execution, Deployment | Compiler and select the Make project automatically option:

Note that automatic compilation in IntelliJ IDEA differs from that in Eclipse. In Eclipse it's not fully automatic, as it is triggered by the save action invoked by the user explicitly, whereas in IntelliJ IDEA it is invoked implicitly when you type in the editor.

This is why, even if the Make project automatically option is enabled, IntelliJ IDEA doesn't perform automatic compilation if at least one application is running: it will reload classes in the application implicitly. In this case you can call Build | Make Project (⌘F9⌘F9⌘BF7⌃F9).

Problems tool window

The Problems tool window appears if the Make project automatically option is enabled in the Compiler settings. It shows a list of problems that were detected on project compilation:

Eclipse compiler

While Eclipse uses its own compiler, IntelliJ IDEA uses the javac compiler bundled with the project JDK. If you must use the Eclipse compiler, navigate to Settings/Preferences | Build, Execution, Deployment | Compiler | Java Compiler and select it as shown below:

The biggest difference between the Eclipse and javac compilers is that the Eclipse compiler is more tolerant to errors, and sometimes lets you run code that doesn't compile.

In situations when you need to run code with compilation errors in IntelliJ IDEA, replace the Make option in your run configuration with Make, no error check:

Shortcuts

IntelliJ IDEA shortcuts are completely different from those in Eclipse.

The table below shows how the top Eclipse actions (and their shortcuts) are mapped to IntelliJ IDEA (you may want to print it out to always have it handy).

Eclipse keymap

For Eclipse users who prefer not to learn new shortcuts, IntelliJ IDEA provides the Eclipse keymap which closely mimics its shortcuts:

Find action

When you don't know the shortcut for some action, try using the Find action feature available via ⇧⌘A⇧⌘A⌘3⌃⇧A⌃⇧A. Start typing to find an action by its name, see its shortcut, or call it:

Coding assistance

Both Eclipse and IntelliJ IDEA provide coding assistance features, such as code completion, code generation, quick-fixes, live templates, etc.

Quick-fixes

To apply a quick-fix in IntelliJ IDEA, press ⌥⏎⌥⏎⌘1⌥⏎⌥⏎:

All quick-fixes are based on inspections configured in Settings | Inspections:

If you want to apply a quick-fix to several places at once (i.e. to a whole folder, module or even a project), you can do it by running the corresponding inspection via Analyze | Run Inspection By Name or by running the whole batch of inspections via Analyze | Inspect Code:

Apart from outright problems, IntelliJ IDEA also recognizes code constructs that can be improved or optimized via the so-called intentions (also available with ⌥⏎⌥⏎⌘1⌥⏎⌥⏎):

Generating code

The key action for generating code is Code | Generate, available via ⌘N⌃N⌘N⌃N:

This action is context-sensitive and is available not only within the editor, but also in the Project Tool Window and the Navigation bar:

Code completion

IntelliJ IDEA provides several different types of code completion, which include:

• Basic completion
• Second basic completion
• Smart completion
• Second smart completion
• Statement completion

To learn more about the differences between these completion types, refer to Top 20 Features of Code Completion in IntelliJ IDEA.

By default, IntelliJ IDEA doesn't show the Documentation popup for the selected item, but you can enable it in Settings/Preferences | Editor | Code Completion | Autopopup documentatoin in (ms):

If you don't want to enable this option, you can manually invoke this popup by pressing F1⌃J⌥Button2 Click⌃Q⌃Q when you need it:

When the caret is within the brackets of a method or a constructor, you can get the info about the parameters by calling Parameter Info with ⌘P⌘P⌃⇧Space⌃⇧Space⌥⇧P:

Templates

You may be used to typing main in the editor and then calling code completion to have it transformed into a main method definition. However, IntelliJ IDEA templates are a little different:

The list of available templates can be found in Settings/Preferences | Editor | Live Templates. There you can also add your own templates or modify any existing ones.

While IntelliJ IDEA suggests templates in code completion results, you can quckly expand any template without using code completion simply by pressing Tab.

Postfix templates

In addition to 'regular' templates, IntelliJ IDEA offers the so-called postfix templates. They are useful when you want to apply a template to an expression you've already typed. For instance, type a variable name, add .ifn and press Tab. IntelliJ IDEA will turn your expression into a if (...==null){...} statement.

To see a complete list of available postfix templates, go to Settings/Preferences | Editor | General | Postfix Completion.

Surround with live template

The surround with templates is another addition that works similarly to live templates but can be applied to the selected code with ⌥⌘J⌥⌘J⌥⌘J⌃⌥J⌃⌥J.

To define your own surround with template, go to Settings/Preferences | Editor | General | Live Templates and use $SELECTION$ within the template text:

$LOCK$.readLock().lock();
try {
   $SELECTION$
       } finally {
   $LOCK$.readLock().unlock();
}

Navigation

The table below roughly maps the navigation actions available in Eclipse with those in IntelliJ IDEA:

Later, when you get used to these navigation options and need more, refer to Top 20 Navigation Features in IntelliJ IDEA.

Refactorings

The following table maps the shortcuts for the most common refactorings in Eclipse with those in IntelliJ IDEA:

To learn more about many additional refactorings that IntelliJ IDEA offers, refer to Top 20 Refactoring Features in IntelliJ IDEA

Undo

Sometimes, refactorings may affect a lot of files in a project. IntelliJ IDEA not only takes care of applying changes safely, but also lets you revert them. To undo the last refactoring, switch the focus to the Project Tool Window and press ⌘Z⌘Z⌘Z⌃Z⌃⇧-.

Search

Below is a map of the most common search actions and shortcuts:

Code formatting

IntelliJ IDEA code formatting rules (available via Settings/Preferences | Editor | Code Style) are similar to those in Eclipse, with some minor differences. You may want to take note of the fact that the Using the Tab char option is disabled by default, the Indent size may be different, etc.

If you would like to import your Eclipse formatter settings, go to Settings/Preferences | Editor | Code Style | Java, click Manage, click Import and select the exported Eclipse formatter settings (an XML file).

Note that if the Eclipse formatter settings cannot be imported, the following error message shows up:

The input file is not a valid Eclipse XML profile.

Click image to close this popup

Click thumbnail to view larger image.

Note that there may be some discrepancies between the code style settings in IntelliJ IDEA and Eclipse. For example, you cannot tell IntelliJ IDEA to put space after (but not before). If you want IntelliJ IDEA to use the Eclipse formatter, consider installing the Eclipse code formatter plugin.

Running and reloading changes

Similarly to Eclipse, IntelliJ IDEA also has Run/Debug Configurations Dialog that you can access either form the main toolbar, or the main menu. Compare the related shorcuts:

As mentioned before, by default IntelliJ IDEA doesn't compile changed files automatically (unless you configure it to do so). That means the IDE doesn't reload changes automatically. To reload changed classes, call the Make action explicitly via ⌘F9⌘F9⌘BF7⌃F9. If your application is running on a server, in addition to reloading you can use the Update application action via ⌘F10⌘F10⌘F10⌃F10⌃F10:

Debugging

The debuggers in Eclipse and IntelliJ IDEA are similar but use different shortcuts:

Working with Application Servers (Tomcat/TomEE, JBoss EAP, Glassfish, WebLogic, WebSphere)

This feature is supported in the Ultimate edition only.

Deploying to application servers in IntelliJ IDEA is more or less similar to what you are probably used to in Eclipse. To deploy your application to a server:

1. Configure your artifacts via Project Structure | Artifacts (done automatically for Maven and Gradle projects).
2. Configure an application server via Settings | Application Servers.
3. Create a run configuration, and then specify the artifacts to deploy and the server to deploy to.

You can always tell the IDE to build/rebuild your artifacts once the have been configured via Build | Build Artifacts.

Working with Build Tools (Maven/Gradle)

IntelliJ IDEA doesn't provide visual forms for editing Maven/Gradle configuration files. Once you've imported/created your Maven/Gradle project, you are free to edit its pom.xml/build.gradle files directly in the editor. Later, you can tell IntelliJ IDEA to synchronize the project model with the changed files on demand, or automatically import changes to the new build files. Any changes to the underlying build configuration will eventually need to be synced with the project model in IntelliJ IDEA.

For operations specific to Maven/Gradle, IntelliJ IDEA provides the Maven Project tool window and the Gradle tool window. Apart from your project structure, these tool windows provide a list of goals/tasks plus a toolbar with the relevant actions.

If you want the IDE to synchronize your changes immediately:

• For pom.xml, enable the corresponding options in Settings | Build, Execution, Deployment | Build Tools | Maven | Importing | Import Maven projects automatically
• For build.gradle, enable the corresponding option in Settings | Build, Execution, Deployment | Build Tools | Gradle | Use auto-import.

For manual synchronization, use the corresponding action on the Maven/Gradle tool window toolbar: .

Running goals/tasks

Use the Maven/Gradle tool window to run any project goal/task. When you do, IntelliJ IDEA creates the corresponding run configuration which you can reuse later to run the goal/task quickly.

It's worth mentioning that any goal/task can be attached to be run before a Run Configuration. This may be useful when your goal/task generates specific files needed by the application.

Both the Maven and Gradle tool windows provide the Run Task action. It runs a Maven/Gradle command similarly to how you'd run it using the console.

Configuring artifacts

If you have WAR artifacts configured in your pom.xml/build.gradle file, IntelliJ IDEA automatically configures the corresponding artifacts in Project Structure | Artifacts.

Note that when you compile your project or build an artifact, IntelliJ IDEA uses its own build process which may be faster, but is not guaranteed to be 100% accurate. If you notice inconsistent results when compiling your project with Make in IntelliJ IDEA, try using a Maven goal or a Gradle task instead.

Working with VCS (Git, Mercurial, Subversion, Perforce)

Configuring VCS roots

When you open a project located under a VCS root, IntelliJ IDEA automatically detects it and suggests adding this root to the project settings. To change version control-related project settings (or manually add a VCS root), go to Settings | Version Control:

IntelliJ IDEA works perfectly with multi-repository projects. Just map your project directories to VCS, and the IDE will take care of the rest. For Git and Mercurial, the IDE will even offer you synchronized branch control, so that you can perform branch operations on multiple repositories simultaneously (for more details, see Using Git Integration).

Editing VCS settings

Every VCS may require specific settings, for example, Path to Git executable, GitHub/Perforce credentials, etc.:

Once you've configured the VCS settings, you'll see the Version Control tool window. You can invoke it any time by pressing ⌘9⌘9⌘9⌥9⌥9.

Checking projects out

To check out a project from a VCS, click Checkout from Version Control on the Welcome Screen, or in the main VCS menu.

Working with local changes

The Local Changes tab of the Version Control tool window shows your local changes: both staged and unstaged. To simplify managing changes, all changes are organized into changelists. Any changes made to source files are automatically included into the active changelist. You can create new changelists, delete the existing ones (except for the Default changelist), and move files between changelists.

To configure ignored files, go to Settings | Version Control, or use the corresponding button in the Version Control tool window.

Working with history

The Log tab of the Version Control tool window lets you see and search through the history of commits. You can sort and filter commits by the repository, branch, user, date, folder, or even a phrase in the description. You can find a particular commit, or just browse through the history and the branch tree:

Working with branches

IntelliJ IDEA lets you create, switch, merge, compare and delete branches. For these operations, either use Branches from the main or context VCS menu, or the VCS operations popup (you can invoke it by pressing ⌃V⌃V⌃V⌥`⌥`, or the widget on the right of the status bar:

All VCS operations are available from the VCS main menu:

Importing an Eclipse project to IntelliJ IDEA

Despite these differences in terms and the UI, you can import either an Eclipse workspace or a single Eclipse project. To do this, click Import Project on the Welcome Screen, or select File | New | Project from Existing Sources in the main menu.

If your project uses a build tool such as Maven or Gradle, we recommend choosing the corresponding option when prompted in the Import Project wizard, and selecting the associated build file (pom.xml or build.gradle):

If you'd like to import your existing run configurations from Eclipse, consider using this third-party plugin.