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下面是来自Dzone 的一篇关于 NetBeans 6.8 Java Editor Reference Guid 文章介绍了NetBeans 6.8 核心的编辑器特性。
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
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
(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.
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
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
Smart Suggestions at the Top
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
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.
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
- Type System.out.p
and wait for code completion to show all fields and methods that start
with "p." All the suggestions will be related to "print."
the Tab key and the editor automatically fills in the "print".
You can continue and type "l" and, after pressing Tab,
the "println" will be added.
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.
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.
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.
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).
quickly see if your code contains unused or missing imports, watch the
error stripes in the righthand margin: orange stripes mark missing or
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
Using the Code Generation Dialog Box
(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.
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
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
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
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
Using Live Templates
Live templates are marked with the icon in the code
You can do one of the following:
- Select a template from the code completion
window and press Enter or
- Type the abbreviation for this
template and press the key that expands this template (by default, Tab).
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:
- Choose Tools > Options > Editor >
- From the Language drop down list, select Java.
The list of abbreviations and associated templates is displayed.
New and Remove buttons to add or remove templates in the list. To
edit an existing template, select the template and edit the code in the
Expanded Text field below the list.
- Choose the key which will be
used to expand the templates. The default key is Tab.
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
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.
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.
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.
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
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
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.
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:
- Select a project, a package, or an individual
file and choose Tools > Analyze Javadoc from the main menu.
The Analyzer window displays suggestions for adding or fixing Javadoc
comments, depending on the scope of your selection.
- Select one
or several checkboxes where you would like to fix Javadoc and click the
Fix Selected button.
Go Over Fixed Problems and use the Up and Down arrows to actually add
your comments. This might be helpful if you selected to fix several
instances at once and now want to revisit the stubs.
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
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.
are displayed automatically by default. However, if you want to view
all hints, choose Source > Fix Code (or press Alt-Enter).
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
You might want to limit
the number of categories for which hints are displayed. To do this:
- Choose Tools > Options > Editor >
the Language drop-down list, select Java and view a list of elements
for which hints are displayed (their checkboxes are selected).
disable hints for some categories, clear the appropriate checkboxes.
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.
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 scope of dependency scans to the Source Root (search for
dependencies only in the source root where the modified class is
located) or current Project.
- Disable dependency scanning. In
this case, the IDE does not scan for dependencies or updates the error
badges when you modify a file.
You can easily surround pieces
of your code with various statements, such as for, while, if,
try/catch, and other.
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
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:
- Choose Tools > Options > Editor >
- From the Language drop-down list, select Java.
Category drop-down list, select the category that you would like to
customize. For example, you can customize the number of blank lines,
the size of tabs and indentation, wrapping style, etc.
the rules for the selected category and preview the result.
Inserting and Highlighting Braces, Brackets, and Quotes
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:
- Choose Tools > Options > Editor >
- Select the Insert Closing Brackets
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.
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.
- The easiest way to collapse a block of code is
to click the gray lines with a minus character in the lefthand margin.
all collapsable blocks in a file, right-click in the editor and
choose Code Folds > Collapse All from the pop-up menu.
the Code Folds > Collapse All pop-up menu, you can choose to collapse
all Javadoc comments or all Java code in a file.
- You can mouse
over the folded elements to quickly review the hidden parts.
To customize the code folding options:
- Choose Tools > Options > Editor >
- To disable code folding, clear Use Code Folding.
Note that code folding is enabled by default.
the blocks of code to be collapsed by default when you open a file.
Customizing Keyboard Shortcuts
In the NetBeans
IDE, choose Tools > Options > Keymap to customize keyboard
shortcuts. You can do this in several ways:
- Select a predefined set of keyboard
shortcuts, which is called Profile.
- Edit particular keyboard
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:
- In the Options > Keymap window, click
- Select the profile you want to use as a base
for your new profile and click Duplicate.
- Enter the new
profile name and click OK.
- Ensure that the new profile is
selected and modify the shortcuts you need.
To edit a shortcut, double-click in the Shortcut field or click the
ellipsis button (...). As you press the sequence of keys, the syntax
for them is added.
If you want to add special characters, such as Tab,
Escape, or Enter, click the ellipsis button (...) again and select the
key from the pop-up window.
- When finished editing, click OK in
the Options window.
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
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.
semantic coloring settings for the Java Editor, choose Tools >
Options > Fonts and Colors.
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:
- In the Options > Fonts and Colors window,
click Duplicate next to the Profile drop-down list.
- Enter the
new profile name and click OK.
- Ensure that the new profile is
currently selected and choose Java from the Language drop-down list.
a category and change the font, font color (Foreground), background
color, and effects for this category.
Use the Preview window to view the results.
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
To export the IDE settings:
- In the Options window (Tools > Options),
- Specify the location and name of the ZIP file that
will be created.
- Select the settings that you want to export
and click OK.
To import the IDE settings:
- In the Options window (Tools > Options),
- Specify the ZIP file with IDE settings or path to
the userdir from a previous version.
- Select the settings
that you want to import and click OK.
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).
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
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
If you decide to rename all the highlighted
instances, use the Instant Rename command (Ctrl-R or choose Refactor
Java Editor provides numerous ways to navigate through
code. See below for several examples that show the navigation features
of the Java Editor.
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
Navigating From the Editor: Go To...
Use the following the "Go
To.." commands located under the Navigate menu item to quickly jump to
- Go To Declaration (Ctr-B, by default).
Hold down the Ctrl key and click the usage of a class, method, or field
to jump to its declaration. You can also place the cursor on the member
(a class, method, or field) and choose Navigate > Go To Declaration
or right-click and choose Navigate > Go To Declaration from the
- Go To Source (Ctrl-Shift-B, by default).
Hold down the Ctrl key and click a class, method, or field to jump to
the source code, if the source is available. You can also place the
cursor on the member (a class, method, or field) and either press
Ctrl-Shift-B or choose Navigate > Go To Source in the main menu.
- Go To Type (Ctrl-O),
Go To File (Alt-Shift-O), and Go To Symbol (Ctrl-Alt-Shift-O).
If you know the name of the type (class, interface, annotation or
enum), file, or symbol to where you want to jump, use these commands
and type the name in the new window. Notice that you can use prefixes,
camel case, and wildcards.
- Go To Line (Ctrl-G).
Enter the line number to which you want to jump.
Jumping to Last Edit
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:
- Go Back (Alt-Left) and Go Forward
To go to the previously edited file or move forward, choose Navigate
< Back or Navigate < Forward or press the corresponding buttons
on the editor toolbar (shown in the figure). The file opens and the
cursor is placed at the location of your last edit. When you click one
of these buttons, you can expand the list of the recent files and click
to navigate to any of them.
Between Files (Ctrl-Tab).
After you press Ctrl-Tab, all open files are shown in a pop-up window.
Hold down the Ctrl key and press several times the Tab key to choose
the file you would like to open.
You can use bookmarks to
quickly navigate through certain places in your code.
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
Using the Navigator
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:
- Choose between different views: Members, Bean
Patterns, Trees, Elements, etc.
- Double-click an element to jump
to the line where it is defined.
- Right-click an element and
apply commands, such as Go to Source, Find Usages, and Refactor.
filters to the elements displayed in the Navigator (use the buttons at
- Type the name of the element that you want to find
(the Navigator window must be active).
Appendix: Icons in the Code
Code Assistance in the NetBeans IDE Java Editor: A Reference Guide