NetBeans IDE Java Editor Reference Guide
NetBeans IDE Java Editor Reference Guide
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The purpose of any IDE is to maximize productivity and support seamless development from a single tool. This reference document describes useful code assistance features, customization options, and navigation capabilities of the NetBeans IDE's Java Editor, which is free and open source. Most of these features have been available in versions earlier than NetBeans IDE 6.8. However, this guide has been written and verified against the latest release, which is NetBeans IDE 6.8.
Note: Download the NetBeans IDE 6.8 Java Editor Refcard from DZone today!
Smart Code Completion
The NetBeans IDE's Java Editor helps you quickly complete and generate code through the "smart" code completion feature. In a general sense, code completion is very useful when you want to fill in the missing code, look at the options available in the context of your application, and generate blocks of code when needed. See below for examples of using code completion.
Invoking Code Completion
Press Ctr-Space (or choose Source > Complete Code from the main menu) to open the code completion box. While you are typing, the list of suggestions shortens. The suggestions listed include those imported in your source file and symbols from the java.lang package.
To customize the code completion settings, select Tools > Options > Editor > Code Completion.
For example, you can set the code completion window to pop up either automatically or only on an as-needed basis. On the Code Completion tab, select the Auto Popup Completion Window checkbox to invoke the code completion window automatically when you are typing certain characters. The default character is ".", but you can add your own characters.
To add characters that invoke the code completion window, select Java from the Language drop-down list and type your characters in the Auto Popup Triggers for Java field. The code completion window will pop up every time you type the specified characters.
When the Auto Popup Completion Window checkbox is disabled, you need to press Ctr-Space each time you want to use code completion.
Smart Suggestions at the Top
In the NetBeans IDE, Java code completion is "smart," which means that the suggestions that are the most relevant for the context of your code are displayed at the top, above the black line in the code completion window.
In the example on the left, the editor suggests inserting the LinkedHashMap constructor from the java.util package.
If the "smart" suggestions are not the ones you want to use, press Ctr-Space again to see a complete list.
Use code completion (Ctr-Space) to complete keywords in your code. The editor analyzes the context and suggests the most relevant keywords.
In the example on the left, the ColorChooserDemo class extends the JPanel class. You can quickly add the keyword extends from the suggested items.
Suggesting Names for Variable and Fields
When you are adding a new field or a variable, use code completion (Ctr-Space) to choose a name that matches its type.
Type a prefix for the new name, press Ctr-Space and select the name you want to use from the list of suggestions.
The editor guesses parameters for variables, methods, or fields and displays the suggestions in a pop-up box.
For example, when you select a method from the code completion window which has one or more arguments, the Editor highlights the first argument and displays a tooltip suggesting the format for this argument. To move to the next argument, press the Tab or Enter keys.
You can invoke the tooltips with method parameters by pressing Ctr-P (or Source > Show Method Parameters) at any time.
Common Prefix Completion
You can use the Tab key to quickly fill in the most commonly used prefixes and single suggestions.
To check out how this feature works, try typing the following:
In the code completion window, icons are used to distinguish different members of the Java language. See Appendix A at the end of this document to see the meanings of these icons.
There are several ways to work with import statements. The editor constantly checks your code for the correct use of import statements and immediately warns you when non-imported classes or unused import statements are detected.
When a non-imported class is found, the error mark appears in the IDE's lefthand margin (this margin is also called the glyph margin). Click the error mark and choose whether to add the missing import or create this class in the current package.
While you are typing, press Ctrl-Shift-I (or choose Source > Fix Imports from the menu) to add all missing import statements at once.
Press Alt-Shift-I to add an import only for the type at which the cursor is located.
When you select a class from the code completion window, the Editor automatically adds an import statement for it, so you do not need to worry about this.
If there are unused import statements in your code, press the warning mark in the Editor lefthand margin and choose either to remove one unused import or all unused imports. In the Editor, unused imports are underlined (see the "Semantic Coloring" section for details).
To quickly see if your code contains unused or missing imports, watch the error stripes in the righthand margin: orange stripes mark missing or unused imports.
When working in the Java Editor, you can generate pieces of code in one of the two ways: by using code completion or from the Code Generation dialog box. Let's take a closer look at simple examples of automatic code generation.
Using the Code Generation Dialog Box
Press Alt-Insert (or choose Source > Insert Code) anywhere in the Editor to insert a construct from the Code Generation box. The suggested list is adjusted to the current context.
In the example on the left, we are going to generate a constructor for the Sample class. Press Alt-Insert, select Constructor from the Code Generation box, and specify the fields that will be initialized by the constructor. The Editor will generate the constructor with the specified parameters.
In the IDE's Java Editor, you can automatically generate various constructs and whole methods, override and delegate methods, add properties and more.
Using Code Completion
You can also generate code from the code completion window. In this example, we use the same piece of code as above to show how you can generate code from the code completion window.
Press Ctrl-Space to open the code completion window and choose the following item: Sample(String name, int number) - generate. The Editor generates a constructor with the specified parameters.
In the code completion window, the constructors that can be automatically generated are marked with the icon and the "generate" note. For more explanations of the icons and their meanings, see Appendix A.
A Live Template is a predefined piece of code that has an abbreviation associated with it. See the examples below that show how you can use live templates.
Using Live Templates
Live templates are marked with the icon in the code completion window.
You can do one of the following:
In the expanded template, editable parts are displayed as blue boxes. Use the Tab key to go through the parts that you need to edit.
Adding or Editing Live Templates
To customize Live Templates:
See this document to know more about the syntax for writing new Live Templates.
Working with Javadoc
Use the following features that facilitate working with Javadoc for your code.
Place the cursor on an element and press Ctr-Shift-Space (or choose Source > Show Documentation). The Javadoc for this element is displayed in a popup window.
In the IDE's main menu, click Window > Other > Javadoc to open the Javadoc window, in which the documentation is refreshed automatically for the location of your cursor.
Creating Javadoc Stubs
Place the cursor above a method or a class that has no Javadoc, type "/**", and press Enter.
The IDE creates a skeletal structure for a Javadoc comment filled with some content. If you have a Javadoc window open, you will see the changes immediately while you are typing.
Using Javadoc Hints
The IDE displays hints when Javadoc is missing or Javadoc tags are needed.
Click the bulb icon on the lefthand margin of the editor to fix Javadoc errors.
If you do not want to see the hints related to Javadoc, choose Tools > Options > Editor > Hints, and clear the Javadoc checkbox in the list of hints that are displayed.
Using Code Completion for Javadoc Tags
Code completion is available for Javadoc tags.
Type the "@" symbol and wait until the code completion window opens (depending on your settings, you may need to press Ctr-Space).
To generate Javadoc for a project, choose Run > Generate Javadoc menu item (or right-click the project in the Projects window and choose Generate Javadoc). The IDE will generate the Javadoc and open it in a separate browser window.
In the example on the right, you can see a sample output of the Generate Javadoc command. If there are some warnings or errors, they are also displayed in this window.
To customize Javadoc formatting options, right-click the project and open the Documenting panel under the Build category. For information about the options on this panel, click the Help button in this window.
To identify the places in your code that need Javadoc comments and quickly insert these comments, you can use the Javadoc Analyzer tool available in the Java Editor.
To analyze and fix Javadoc comments:
While you are typing, the Java Editor checks your code and provides suggestions of how you can fix errors and navigate through code. The examples below show the types of hints that are available in the Editor and how to customize them.
Using Hints to Fix Code
For the most common coding mistakes, you can see hints in the lefthand margin of the Editor. The hints are shown for many types of errors, such as missing field and variable definitions, problems with imports, braces, and other. Click the hint icon and select the fix to add.
Hints are displayed automatically by default. However, if you want to view all hints, choose Source > Fix Code (or press Alt-Enter).
For example, try typing "myBoolean=true". The editor detects that this valiable is not defined. Click the hint icon and see that the Editor suggests that you create a field, a method parameter, or a local variable. Select
You might want to limit the number of categories for which hints are displayed. To do this:
Note: On the Hints tab, you can also disable or limit the scope of dependency scans (Dependency Scanning option). These steps can singificantly improve the performance of the IDE.
The IDE detects compilation errors in your Java sources by locating and recompiling classes that depend on the file that you are modifying (even if these dependencies are in the files that are not opened in the editor). When a compilation error is found, red badges are added to source file, package, or project nodes. Dependency scanning within projects can be resource consuming and degrade performance, especially if you are working with large projects.
To improve IDE's performance, you can do one of the following:
You can easily surround pieces of your code with various statements, such as for, while, if, try/catch, and other.
Select a block in your code that you want to surround with a statement and click the bulb icon in the lefthand margin (or press Alt-Enter). The editor displays a list of suggestions from which you select the statement you need.
General Editor Features
Use the following general features in the IDE for code formatting, braces, brackets, quotes, code folding, and keyboard shortcuts.
Choose Source > Format or press Alt-Shift-F to format the entire file or a selection of code. The IDE formats the code in accordance with the specified formatting settings.
To customize the formatting settings for Java code:
Inserting and Highlighting Braces, Brackets, and Quotes
By default, the IDE automatically inserts matching pairs of braces, brackets, and quotes. When you type an opening curly brace and then press Enter, the closing brace is added automatically. For (, [, ", and ', the editor inserts a matching pair right away.
If, for some reason, this feature is disabled, enable it as follows:
The editor also highlights matching pairs of braces, brackets and quotes. For example, place the cursor before any brace or bracket and, if it has a matching pair, both will be highlighted in yellow. Single brackets of any type are highlighted in red and the error mark is displayed in the lefthand margin.
To customize the highlight colors, choose Tools > Options > Fonts & Colors > Highlighting.
In the Java Editor, you can quickly collapse and expand blocks of code, such as method declaration, Javadoc comments, import statements, etc. Collapsable blocks are shown with gray lines and plus/minus signs near the lefthand margin of the editor.
To customize the code folding options:
Customizing Keyboard Shortcuts
In the NetBeans IDE, choose Tools > Options > Keymap to customize keyboard shortcuts. You can do this in several ways:
You can save customized sets of your shortcuts as profiles. Then, you can switch from one profile to another to quickly change multiple settings. For example, to create a custom profile of keyboard shortcuts:
To find a shortcut for a specific command, type the command name in the Search field. To find a command by a combination, insert the cursor in the Search in Shortcuts field and press the shortcut key combination.
Semantic Coloring and Highlighting
The IDE's Java Editor shows code elements in distinct colors, based on the semantics of your code. With semantic coloring, it becomes easier for you to identify various elements in your code. In addition to coloring, the Java Editor highlights similar elements with a particular background color. Thus, you can think of the highlighting feature as an alternative to the Search command, because in combination with error stripes, it gives you a quick overview of where the highlighted places are located within a file.
To customize semantic coloring settings for the Java Editor, choose Tools > Options > Fonts and Colors.
The IDE provides several preset coloring schemes, which are called profiles. You can create new profiles with custom colors and quickly switch between them.
It is very convenient to save custom colors in new profiles. For example, do the following:
Note: All NetBeans IDE settings and profiles are stored in the NetBeans userdir (refer to the FAQ on how to locate the userdir for your operating system). When upgrading to newer versions of NetBeans, you can export old settings and import them to the newer version.
To export the IDE settings:
To import the IDE settings:
On the left, you can see an example of a coloring scheme. Depending on your custom settings, your colors might look differently than those shown in the screenshot.
Distinct colors are used for keywords (blue), variables and fields (green), and parameters (orange).
References to deprecated methods or classes are shown as strikethrough. This warns you when you are going to write code that relies on deprecated members.
Unused members are underlined with a gray wavy line. Comments are displayed in gray.
The IDE highlights usages of the same element, matching braces, method exit points, and exception throwing points.
If you place the cursor in an element, such as a field or a variable, all usages of this element are highlighted. Note that error stripes in the Editor's righthand margin indicate the usages of this element in the entire source file (see Error Stripes). Click the error stripe to quickly navigate to the desired usage location.
If you decide to rename all the highlighted instances, use the Instant Rename command (Ctrl-R or choose Refactor > Rename).
The Java Editor provides numerous ways to navigate through code. See below for several examples that show the navigation features of the Java Editor.
Error stripes in the righthand margin of the editor provide a quick overview of all marked places in the current file: errors, warnings, hints, highlighted occurences, and annotations. Note that the error stripe margin represents an entire file, not just the part that is currently displayed in the editor. By using error stripes, you can immediately identify whether your file has any errors or warnings, without scrolling through the file.
Click an error stripe to jump to the line that the mark refers to.
Navigating From the Editor: Go To...
Use the following the "Go To.." commands located under the Navigate menu item to quickly jump to target locations:
Jumping to Last Edit
To quickly return to your last edit, even if it is in another file or project, press Ctrl-Q or use the button in the top left corner of the Java Editor toolbar. The last edited document opens, and the cursor is at the position, which you edited last.
Switching Between Files
There are two very handy features that allow you to switch between open files:
You can use bookmarks to quickly navigate through certain places in your code.
Press Ctrl-Shift-M (or right-click the left margin and choose Bookmark > Toggle Bookmark) to bookmark the current line. The bookmarked line is shown with a small blue icon in the left margin (see the figure).
To remove the bookmark, press Ctrl-Shift-M again.
To go to the next bookmark, press Ctrl-Shift-Period, to go to the previous bookmark, press Ctrl-Shift-Comma.
Using the Navigator
The Navigator window provides structured views of the file you are working with and lets you quickly navigate between different parts of the file.
To open the Navigator window, choose Window > Navigating > Navigator or press Ctrl-7.
In the Navigator window, you can do the following:
Appendix: Icons in the Code Completion Window
|Icon||Meaning||Variants (if any)||
|Constructor||New constructor (generate)|
|Package private constructor|
|Package private field|
|Static field||Protected static field|
|Private static field|
|Package private static field|
|Package private method|
|Static method||Protected static method|
|Private static method|
|Package private static method|
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