IntelliJ IDEA Essentials

From the get-go, IntelliJ IDEA has followed a simple, overriding principle: if it doesn't make a Java developer more productive, it doesn't go in the product. Period. With a tight focus on what a professional Java developer needs, IntelliJ IDEA can make you as productive as you're capable of being. This Refcard is about unlocking that power. Focused on IntelliJ IDEA 15, which will have a full release in fall of 2015, most of the tips, tricks, and shortcuts in this Refcard will work for you regardless of your version of the IDE.

The IntelliJ IDEA editor is unique in a number of ways, most notably that you can invoke almost any IDE feature without leaving it, which allows you to organize a layout where you have more screen space because auxiliary controls like toolbars and windows are hidden.

Figure 1:The IntelliJ IDEA UI

Accessing a tool window via its shortcut moves the input focus to it, so you can use all keyboard commands in its context. When you need to go back to the editor, press Esc.

When you need to just focus on the code, try the Distraction Free Mode. It removes all toolbars, tool windows, and editor tabs. To switch to this mode, select View → Enter Distraction Free Mode.

An alternative to Distraction Free Mode may be hiding all tool windows by pressing Ctrl+Shift+F12 (Shift+Cmd+F12 for OS X). Restore the layout to default by pressing the shortcut again.

The Navigation Bar is a compact alternative to the Project tool window. To access the Navigation Bar, press Alt+Home (Cmd+Up for OS X).

Figure 2:The IntelliJ IDEA Navigation Bar

Most components in IntelliJ IDEA (both tool windows and popups) provide speed search. This feature allows you to filter the list or navigate to a particular item by using a search query.

Figure 3:IntelliJ IDEA Speed Search

Accessing Basic Completion by pressing Ctrl+Space offers basic suggestions for variables, types, methods, expressions, and so on. When you call Basic Completiontwice, it shows you more results, including private members and non-imported static members.

The Smart Completion feature is aware of the expected type and data flow and offers the option relevant to the context. To call Smart Completion, press Shift+Ctrl+Space. When you call Smart completion twice, it shows you more results, including chains.

To overwrite the identifier at the caret, instead of just inserting the suggestion, press Tab. This is helpful if you’re editing part of an identifier, such as a file name.

To let the IDE complete a statement for you, press Shift+Ctrl+Enter (Shift+Cmd+Enter for OS X). Statement Completionwill automatically add missing parentheses, brackets, braces and the necessary formatting.

Parameter Info

If you want to see the suggested parameters for any method or constructor, just press Ctrl+P (Cmd+P for OS X). IntelliJ IDEA shows parameter info for every overloaded method or constructor and highlights the best match for the parameters already typed.

The Postfix Completion feature lets you transform an already typed expression to another one based on the postfix you type after a period, the expression type, and its context.

Since in IntelliJ IDEAyou can undo refactorings and revert changes from Local History, it makes no sense to ask you to save your changes every time—IntelliJ IDEA autosaves your changes for you.

Editor shortcuts include:

Other useful editor actions:

To expand a selection based on grammar, press Ctrl+W (Cmd+W for OS X). To shrink it, press Shift+Ctrl+W (Shift+Cmd+W for OS X).

Recent files

Most of the time you work with a finite set of files and need to switch between them quickly. A real time-saver here is an action called Recent Files invokedby pressing Ctrl+E (Cmd+E for OS X). By default, the focus is on the last accessed file. You can open any tool window through this action.

Figure 4:IntelliJ IDEA Recent Files

Navigate to Class is available by pressing Ctrl+N (Cmd+O for OS X) and supports sophisticated expressions, including camel humps, path, line navigate to, middle name matching, and many more. If you call it twice, it shows you the results out of the project classes.

Navigate to File works similarly by pressing Ctrl+Shift+N (Cmd+Shift+O for OS X) but is used for files and folders. To navigate to a folder, end your expression with the “/” character.

Navigate to Symbol is available by pressing Ctrl+Alt+Shift+N (Alt+Cmd+O for OS X) and allows you to find a method or field by its name.

Structure

When you are not switching between files you are probably navigating within a file. The shortest way to do it is to press Ctrl+F12 (Cmd+F12 for OS X). The popup shows you the structure of a file and allows you to quickly navigate to any item.

Figure 5:IntelliJ IDEA File Structure Navigation

Select In

If you need to open the file in a particular tool window (or Finder/Explorer) you can do it via the Select Inaction by pressing Alt+F1.

Figure 6:IntelliJ IDEA Select In

Navigation shortcuts include:

Quick Pop-ups are helpful for checking additional information related to the symbol at the caret. Here is a list of pop-ups you should know if you want to be more productive.

Quick Pop-ups are available for symbols in the editor; however, they are also available for items in any other list via the same shortcuts.

IntelliJ IDEA offers a comprehensive set of automated code refactorings that lead to significant productivity gains when used correctly. Firstly, don't bother selecting anything before you apply a refactoring. IntelliJ IDEAis smart enough to figure out what statement you’re going to refactor, and only asks for confirmation if there are several possible choices.

A real time-saver is the ability to extract part of a string expression with the help of the Extract... refactorings. Just select a string fragment and apply a refactoring to replace all of the selected fragment usages with the introduced constant or variable.

Find Usages helps you quickly find all pieces of code referencing the symbol at the caret (cursor), no matter if the symbol is a class, method, field, parameter, or another statement. Just press Alt+F7 and get a list of references grouped by usage type, module, and file.

If you want to set custom options for the Find Usages algorithm, press Shift+Alt+Ctrl+F7 (Shift+Alt+Cmd+F7 for OS X) or click the first button on the right panel with search results.

If what you’re looking for is plain text, use Find in Pathby pressing Shift+Ctrl+F (Shift+Cmd+F for OS X).

Inspections are built-in static code analysis tools that help you find probable bugs, locate dead code, detect performance issues, and improve the overall code structure.

Most inspections not only tell you where a problem is, but provide quick fixes to deal with them right away. Press Alt+Enter to choose a quick-fix.

The editor lets you quickly navigate between the highlighted problems via keyboard shortcuts. Press F2 to go to the next problem and Shift+F2 to go to the previous one.

Inspections that are too complex to be run on the fly are available when you perform code analysis for the entire project. You can do this one of two ways: by selecting Analyze → Inspect Code from the menu, or by selecting Analyze → Run Inspection by Name to run the inspection by its name.

While inspections provide quick-fixes for code that has potential problems, intentions help you apply automatic changes to code that is correct. To get a list of intentions applicable to the code at the caret, press Alt+Enter.

IntelliJ IDEAautomatically applies a code style you've configured in the Settings → Code Style menu as you edit and in most cases you don’t need to call the Reformat Code action explicitly.

Useful formatting shortcuts:

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

Figure 7: IntelliJ IDEA Version Control Operations

Once you’ve configured the VCS settings, you’ll see the Version Controltool window. You can switch to it anytime by pressing Alt+9 (⌘9 for OS X).

The Local Changes tab of the Version Controltool window shows your local changes: both staged and unstaged.

Useful VCS shortcuts:

Branches

To perform an operation on a branch, use either Branches from the main or context menu, the VCS operations popup, or the widget on the right of the status bar.

For multiple repositories, IntelliJ IDEA performs all VCS operations on all branches simultaneously, so you don't need to switch between them manually.

Shelves, Stashes, and Patcheshelp you when you need to store some of the local changes without committing them to the repository. You can then switch to the repository versions of the files, and then come back to your changes later.

By default,IntellIJ IDEA doesn’t automatically compile projects on saving. To compile a project, select Build → Make Project and press Ctrl+F9 (Cmd+F9 for OS X).

Once you’ve created a Run/Debug configuration by selecting Run → Edit Configurations…, you’re able to run and debug your code.

While in the debug mode, you can evaluate any expression by using the Evaluate expression tool, which is accessed by pressing Alt+F8. This tool provides code completion just as in the editor, so it’s easy to enter any expression.

Sometimes it happens that you want to step into a particular method but not the first one which will be invoked. In this case, use Smart step into by pressing Shift+F7 (Cmd+F7 for OS X) to choose a particular method.

If you want to “rewind” while debugging you can do it via the Drop Frame action. This is particularly helpful if you mistakenly stepped too far. This will not revert the global state of your application, but will at least let you revert to a previous stack frame.

Reloading Changes and Hot Swapping

Sometimes you need to insert minor changes into your code without shutting down the process. Since the Java VM has a HotSwap feature, the IDE handles these cases automatically when you call Make.

To deploy your application to a server:

Configure yourartifacts by selecting Project Structure → Artifacts (done automatically for Maven and Gradle projects).

Configure an application serverby selecting Settings → Application Servers.

Create a run configuration by selecting Run → Edit Configurations…, then specify the artifacts to deploy and the server to deploy it to.

You can always ask the IDE to build/rebuild your artifacts (once they’re configured) by selecting Build → Build Artifacts…

When you need to apply changes in the code to a running application, in addition to Make you can use the Update action by pressing Ctrl+F10 (Cmd+F10 for OS X). This action is only available for the Exploded artifact type. Based on your choice, it can update resources or update classes and resources. When the Update action is applied in the Debug mode, it uses HotSwap; otherwise, it uses Hot redeployment.

Once you’ve imported/created your Maven/Gradleproject, you are free to edit its pom.xml/build.gradle files directly via the editor. Any changes to the underlying build configuration will eventually need to be synced with the project model in IntelliJ IDEA.

If you want the IDE to synchronize your changes immediately, perform the following:

For pom.xml, enable the corresponding option 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: