IntelliJ IDEA

By Hamlet D'Arcy

ABOUT INTELLIJ IDEA

Software developers know the importance of using the best tool for the job. Often this means choosing a world-class integrated development environment (IDE), which JetBrains IntelliJ IDEA certainly is. But the best developers don't just have the right tools, they are experts in those tools. This is a guide to becoming that expert. The basics of navigating and understanding IDEA are covered; but this guide is really about unlocking all the powerful features of the tool, possibly making you orders of magnitude more productive than you were before.

Getting Yourself Oriented

The three most important elements of the IDE are the Editor pane (a), where your code is shown, the Project pane (b), where your project's contents are shown, and the Structure pane (c), where the details of the open object are shown.

Editor Pane: Shows the currently active file, with recently viewed files in the tab bar. IDEA shows the most recently used files in the tabs, and there is seldom a need to manually close tabs. If the maximum number of tabs is reached, then the oldest tab is closed when a new tab is opened. Also, there is seldom a need to save a file; file saving is performed automatically in the background. IDEA supports syntax highlighting for many languages, but is also language aware and shows syntax errors as they occur. Navigate faster by learning these commands: Edit faster by learning these commands:

Back	Ctrl+Alt+Left		Move back to the last cursor position
Forward	Ctrl+Alt+Right		Move forward to the next cursor position
Next Tab	Alt+Right		Activate tab to the right of the active one
Previous Tab	Alt+Left		Activate tab to the left of the active one
Goto Line	Ctrl+G		Go to a specific line in the active file
Goto Last Edit Location	Ctrl+Shift+Backspace		Go to the position of the last edit

Edit faster by learning these commands:

Project Pane: Shows the contents of the current project, allowing you to view the project as files, packages, or scopes (more about this later). Objects in the project view visually indicate their type with an icon (which also appears on the editor tabs).

Find objects faster by learning what the icons mean:

	Class		Class with main( ) (indicated by green triangle)
	Interface		public
	Abstract Class		protected
	Enumeration		package
	Exception		private
	Annotation		Read Only (indicated by lock)
	Test Case (indicated by red and green triangles)		Not in version control (object name appears in red)
	Final Class (Indicated by pin)		In version control (object name appears black, or blue if edited)

Properly configuring the Project pane makes it more effective:

	Autoscroll to Source	When an object or method is clicked in the Project pane, that item is opened in the Editor pane.
	Autoscroll from Source	When an item is opened in the Editor pane, that item is scrolled to in the Project pane
	Show structure	Shows the Structure pane (explained next) as a window nested within the Project pane
	Show/Hide Members	Shows the methods and properties of objects within the Project pane
	Sort by type	Sorts the Java classes by type from the most abstract to the most concrete

Structure Pane: Shows the structure of the active file, including methods, properties, and inner classes. Leaving this pane open helps you quickly locate the desired point within a class. Make this pane more useful by tweaking the configuration options:

	Autoscroll to source		Show properties
	Autoscroll from source		Show inherited
	Sort by visibility		Show fields
	Sort alphabetically		Show non-public
	Group Methods by defining type

Finding What You Need

IDEA sets itself apart from other products by offering incredibly advanced ways to find objects and files within large projects. Mastering the act of finding what you need is key to faster development.

The navigation bar is a useful alternative to the Project pane. This horizontal bar provides breadcrumb style navigation based on the active file. To navigate to a different package, simply click the + to expand a node higher up in the tree. The navigation bar can be a faster alternative to the Project pane.

Navigating a single class is done through the Structure pane (described earlier) and the file structure popup.

File Structure Popup: (Ctrl+F12) allows quick navigation to methods, fields, and properties. Use the Up/Down arrows to select an entry, or (better) use the search as you type field. Just start typing to narrow the list down. The field provides wildcard and camel case matching. Selecting an entry scrolls the active file to that entry's declaration.

Navigating large object oriented codebases is greatly simplified by learning these commands:

Ctrl+B / Middle Click	Go to declaration. Navigates to the declaration of the selected instance or type.
Ctrl+Alt+B	Go to implementers or overriders of the selected method. Clicking the icon in the left gutter performs the same action
Ctrl+U	Go to the parent of the selected method or type. Clicking the icon in the left gutter performs the same action
Ctrl+Mouse Over	Shows the declaration of a local variable or field in a popup window
Ctrl+H	Opens the Type Hierarchy pane for the active class. This pane explores the super and subclasses of the current object with a variety of different views
Ctrl+Shift+H	Opens the Method Hierarchy pane for the active method. This pane explores the definitions and implementations of the current method.
F4	Jump to Source. Many tool windows display objects within project. Used from a tool window, F4 universally opens the element from the tool in the editor. If you're in the Ant, Hierarchy, or Find window, then F4 will open the selection in the editor pane.

Finding usages is an important feature of any IDE. Being Java aware, IDEA offers more intelligent searching than simple string matching.

Highlight Usages in File (Ctrl+Shift+F7) takes the current mouse selection and highlights all occurrences of that element in the file. The Editor pane and the right gutter provide visual keys to where the occurrences appear. Use F3 and Shift+F3 to jump to the next and previous occurrence.

Show Usages Popup (Ctrl+Alt+F7) takes the current mouse selection and searches the project for any references made to the field or type. Results appear in an in-editor popup window.

Show Usages in Find Panel (Alt+F7) behaves the same as the Show Usages Popup, except that results are displayed in the Find pane. Learning to operate the Find pane with the keyboard helps you move faster to the intended object.

		Rerun the last find
Shift+Esc		Close the Find pane
Ctrl+NumPad +		Expand all the nodes in the list
Ctrl+NumPad -		Collapse all the nodes in the list
Ctrl+Alt+Up		Navigate to the previous occurrence
Ctrl+Alt+Down		Navigate to the next occurrence

Search Structurally (Ctrl+Shift+S) and Replace Structurally (Ctrl+Shift+M) allows searching (and replacing) references using patterns. Again, this is Java aware and done structurally, and is not just text string search and replace. This very rich feature is best explained with an example. Here are the steps to find any factory methods within the project (ie, methods whose name starts with "create"):

• Open Search Structurally (Ctrl+Shift+S)
• Click "Copy the existing template" and select method calls, which is $Instance$.$MethodCall$($Parameter$)
• Click "Edit variables" and select MethodCall
• For the MethodCall variable, enter "create.*" in the Text / Regular Expression. This is the regular expression for the word create followed by any number of other characters
• Click "Find" to open the Find pane showing all the factory methods

Scopes

Often, you only want to search a subset of your project, for instance just the test source or just the production source. IDEA provides Scopes to create smaller filesets used in searching, replacing, and inspections. Some default scopes are "Project Production Files", "Project Test Files", and "Changed Files". Fine tune your searching by defining your own scope, perhaps based on a set of packages. Scopes can also be helpful to speed up searches on large projects. Here are the steps to define a scope:

1. Open Settings (Ctrl+Alt+S) and select Scopes (5)
2. Click to create a new scope
3. Select a package to include from the project browser. Use include and include recursively to broaden the fileset, and exclude and exclude recursively to narrow the fileset
4. Save. New Scope is now available for many operations

Finding Documentation

There are many ways to find documentation on objects within your project or dependent libraries. Master the following commands to get the information you need without leaving the IDEA:

Runing and Debuging Your Project

Running and debugging the project is an essential part of any IDE. The easiest way to run an application is to right click the object within the Editor pane and select Run. This works for classes with main() and test cases. You can also right click the object and do the same thing in the Project pane. To run tests in an entire package simply right click the package.

Run targets are managed by IDEA using the Run/Debug Configurations window. If you need advanced settings or VM parameters then use this window to adjust them. Open the window by clicking Edit Configurations within the toolbar's dropdown.

Common run targets can be saved here for future runs.

Running an entry point will display the Run pane. This pane provides diagnostics on the running process. Get the information you need from running processes by learning to use the pane:

Ctrl+F5		Run the last target
		Pause execution
Ctrl+F2		Stop execution
Ctrl+Break		Dump Thread information to a new window or clipboard
Ctrl+Alt+Up		Move Up Stack Trace, opening the Editor pane to the exception location
Ctrl+Alt+Down		Move Down Stack Trace, opening the Editor pane to the exception location

When debugging an application, IDEA provides a variety of ways to set breakpoints and watchpoints. The easiest is to click the left gutter of the line or method on which you want a breakpoint. More advanced breakpoints are available through the Breakpoints window (Ctrl+Shift+F8).

Once stopped on a breakpoint, the Debug pane will open. This pane provides features common to all debuggers, as well as more advanced, uncommon actions.

Alt+F10		Show Execution Point
F8		Step Over
F7		Step Into
Alt+Shift+F7		Force Step Into
Shift+F8		Step Out
		Drop Frame
Ctrl+Alt+Up		Previous Stack Frame
Ctrl+Alt+Down		Next Stack Frame
Alt+F9		Run to Cursor

Once in the debugger, several panels provide different views of the application state. The Frames Panel shows the current stack frames on the selected thread, and you can navigate quickly between frames and threads. The Variables Panel shows any variables currently in scope. And the Watches Panel shows expanded information on selected variables. When entering variables to watch, autocompletion and smart-type both work.

Expression Evaluation (Alt+F8) allows quick execution of code snippets or blocks. From this window you can reference any in-scope variable of the application. It works a bit like a REPL window open with the current breakpoint's environment, and is most useful in code fragment mode, where you can evaluate multi-line statements.

Code Coverage: IDEA offers built in code coverage using the EMMA open-source toolkit. Enable coverage tracking in the Code Coverage tab of the Run/Debug Configurations window. Coverage results appear in several places:

Code Coverage Data (Ctrl+Alt+F6) displays a list of previous runs, and selecting an entry shows the coverage data for that run. You can use this to compare coverage between subsequent runs.

Write Less Code

Typing less to produce more is a feature of any modern IDE. IDEA provides top tier code completion support, as well as many other code generation, file template, and refactoring features.

Code Completion: Leveraging code completion is essential to productivity:

Code Generation: Letting IDEA infer the code you want to create and drop in the appropriate template can be a huge time saver.

Generate (Alt+Insert) provides its own set of powerful options for code generation:

Live Templates are fragments of commonly occurring code, which can be inserted into the active file in a variety of ways. Learning the live templates will save you many, many keystrokes. A full list is available in Settings (Ctrl+Alt+S) Live Templates (K).

To insert a live template, press Ctrl+J followed by the following keys:

Surround with Live Template (Ctrl+Alt+J) will surround the current selection with a block of code. Some of the useful surrounds are:

Live Template in Multiple Languages: Many live templates exist for languages other than Java. JSP, XML, Spring definitions, and more all exist. Here are some examples of templates from other platforms and toolsets:

Refactoring: IDEA offers excellent refactoring support. Refactoring is aware of comments, reflection, Spring, AOP, JSP, and more. When the refactoring features are unsure on the safety of a refactoring, a preview mode is invoked so that you can verify the changes. Refactoring works on more than just Java code too: many refactorings exists for XML files as well as other languages. Learning the refactoring tools (and reading the refactoring literature, for that matter) is well worth your time. Here are some of the more common refactorings:

Improve Your Project's Quality

IDEA's features aren't just about writing code faster, they are also about coding more accurately. Understanding the intentions, inspections, and analysis tools are key to keeping code high quality.

Intentions: Keeps code clean by flagging potential problems in the Editor pane as they occur, and then offers an automated solution. An available intention is signaled by a lightbulb appearing in the left gutter, and the suggested fix can be applied by pressing Alt+Enter. There are several types of intentions:

• "Create from usage" intentions allow you to use new objects and methods without defining them first. Need a new method? Just call it from code and IDEA will prompt you to create it, inferring the parameter and result types. This works for classes, interfaces, fields, and variables. If the missing reference is in all capital letters, then IDEA will even create a constant for you.
• "Quick fix" intentions find common mistakes and makes context-based suggestions on how to fix them. Examples of issues flagged with a quick fix are assigning a value to the wrong type or calling a private method.
• "Micro-refactorings" fix code that compiles but could be improved. Examples are removing an unneeded variable and inverting an if condition.

Some of the intentions or fixes might violate your coding standard. Luckily, they can all be configured within Settings (Ctrl+Alt+S) Intentions (Q)

Intentions and Quick Fixes are indicated by different icons in the left gutter, but in practice there is little need to differentiate between the two:

	Intention available
	Quick Fix available

Inspections: Keeps code clean by detecting inconsistencies, dead code, probable bugs, and much, much more. The near-1000 default inspections can do a lot to enforce common idioms and catch simple bugs across the project. There are way too many inspections to list, but here are examples to provide a flavor of what inspections can do:

• Flag infinite recursion or malformed regular expression
• Catch error handling issues like continue within finally block or unused catch parameter
• Find threading issues like await() outside a loop or non-thread safe access
• Error on Javadoc issues like missing tags or invalid links

Inspections work with many languages and tools beyond the Java language, like Spring, JSF, Struts, XML, JavaScript, Groovy, and many others. The inspection set is highly configurable through Settings (Ctrl+Alt+S) Errors (6). Each inspection can carry its own set of options, and most can be shown as warnings or errors within the IDE. When an inspection violation is shown in the right gutter, Alt+Enter triggers the suggestions to be shown.

Some inspections appear within the Editor pane, while others appear within the Inspection pane when they are run as a batch. To run inspections for a scope, go to Analyze -> Inspect Code in the menu.

Inspection settings can be configured and shared across the team. An "IDE" inspection profile is saved within the user's $HOME directory, but a "Project" profile is saved within the IDEA project file. This means a shared, version controlled project file can be created which contains the team's inspections.

Code Analysis: Provides several different views of dependencies and duplicates within your project. These tools help you modularize your code and find areas of potential reuse. All of the following features are available from the Analyze menu.

The Dependency Viewer provides a split tree-view of your project with a list panel at the bottom. From here you can navigate the dependencies or mark certain undesirable dependencies as illegal. Which analysis feature chosen determines what the Viewer displays:

Not all analysis tools report to the Dependency Viewer, however. Module Dependencies uses a separate panel to display dependencies across all the included modules within the project. This is useful for multi-module projects. Dependency Matrix launches the Dependency Structure Matrix in a separate window. This tool helps you visualize module and class dependencies across the project using a colored matrix.

Locate Duplicates: Finds suspected copy and pastes within your project or desired scope. Use this to find and consolidate duplicate modules or statements. The results are displayed in the Duplicates pane, which ranks the copy/paste violations and allows you to extract methods on the duplicates by simply clicking the Eliminate duplicates icon ().

Work As A Team

IDEA includes many features that allow team members to collaborate effectively.

Version Control (VC) integration exists for Subversion, CVS, Perforce, StarTeam, and Visual SourceSafe. When enabled, local changes appear as a blue bar in the left gutter:

Clicking the blue bar displays some VC options, including a quick line diff (displayed), a rollback of the line changes, or a full file diff in the IDEA Diff Viewer. More VC options are available from the menu or by right-clicking the active editor:

Local History can be used even if you don't have version control. IDEA keeps track of saves and changes to files, allowing you to rollback to previous versions if desired. Older versions can also be labeled, making it easy to find previous save points.

Shared Project: The IDEA project can be put in version control, keeping all environments up to date as changes are made. Use this guide to the project files to determine what files need to be shared:

File Templates: Shared file templates provide a common starting point for frequently typed code. Templates exist, and can be changed, for creating new classes, interfaces, and enumerations. Templates for includes, like a copyright notice, can also be stored and shared, as well as code templates, like default catch statements and method bodies. Modify the file templates in Settings (Ctrl+Alt+S) File Templates (L).

Ant Integration: Many projects use Ant as a common build script, and IDEA offers integration with it. Features include syntax highlighting, code completion, and refactorings. Several inspections and intention settings are also available. Use the Ant Build Window to run one or several Ant targets. For larger projects with many targets, use the filter targets feature to hide uncommon targets. The Maven build system is also supported.

IDE Talk: IDEA ships with an instant messenger client integrated into the IDE, called IDETalk. Messages can be exchanged with IDEA users on your LAN or anyone with a Jabber account, such as Google Talk. Beyond normal IM features, IDEA provides some developer specific features as well:

Endless Tweaking Awaits

A massive amount of configuration options are available in Settings (Ctrl+Alt+S). Beyond that, you may wish to experiment with different plugins. Plugins are installed and managed using Settings (Ctrl+Alt+S) Plugins (U). Many plugins exist, adding features like SQL, Hibernate, and Ruby support. JetBrains holds plugin contests annually, so check the site periodically.

About The Author

Hamlet D'Arcy

Hamlet D'Arcy has been writing software for about a decade, and has spent considerable time coding in C++, Java, and PHP. He's passionate about learning new languages and different ways to think about problems, and recently he's been discovering the joys of both Groovy and Scheme. He's an active member of the Groovy Users of Minnesota and the Object Technology User Group, is involved with a few open source projects, blogs regularly at http://hamletdarcy.blogspot.com, and can be contacted at hamletdrc@gmail.com.

Recommended Book

For new users, IntelliJ IDEA in Action is a logically organized and clearly expressed introduction to a big subject. For veterans, it is also an invaluable guide to the expert techniques they need to know to draw a lot more power out of this incredible tool. You get a broad overview and deep understanding of the features in IntelliJ IDEA.

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