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| Frequently Asked Questions on JDT |
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| <h1> |
| Frequently Asked Questions on JDT |
| </h1> |
| <h3> |
| Can I use a Java compiler other than the built-in one (javac for example) |
| with the workbench? |
| </h3> |
| <p> |
| |
| No. The JDT provides a number of sophisticated features including fully |
| automatic incremental compilation, code snippet evaluation, code assist, |
| type hierarchies, and hot code replace. These features require special |
| support found in the workbench Java compiler (an integral part of the |
| JDT's incremental project builder), but not available in standard Java |
| compilers. |
| </p> |
| <h3> |
| Where do Java packages come from? |
| </h3> |
| <p> |
| A project contains only files and folders. The notion of a Java package |
| is introduced by a Java project's class path (at the UI, the Package |
| Explorer presents the packages as defined by the classpath). |
| <strong>Tip:</strong> If the package structure is not what you expect, |
| check out your class path. The Java search infrastructure only finds |
| declarations for and references from Java elements on the class path. |
| </p> |
| <h3> |
| |
| When do I use an internal versus an external JAR library file? |
| </h3> |
| <p> |
| An internal resource resides in some project in the workbench and is |
| therefore managed by the workbench; like other resources, these resources |
| can be version managed by the workbench. An external resource is not part |
| of the workbench and can be used only by reference. For example, a JRE is |
| often external and very large, and there is no need to associate it with |
| a VCM system. |
| </p> |
| <h3> |
| When should I use source folders within a Java project? |
| </h3> |
| <p> |
| Each Java project locates its Java source files via one or more source |
| type entries on the project's class path. Use source folders to organize |
| the packages of a large project into useful grouping, or to keep source |
| code separate from other files in the same project. Also, use source |
| folders if you have files (documentation for example) which need not be |
| on the build path. |
| </p> |
| |
| <h3> |
| What are source attachments, How do I define one? |
| </h3> |
| <p> |
| Libraries are stored as JAR files containing binary class files (and |
| perhaps other resources). These binary class files provide signature |
| information for packages, classes, methods, and fields. This information |
| is sufficient to compile or run against, but contains far less |
| information that the original source code. In order to make it easier to |
| browse and debug binary libraries, there is a mechanism for associating a |
| corresponding source JAR (or ZIP) file with a binary JAR file. |
| </p> |
| <h3> |
| Why are all my resources duplicated in the output folder (bin, for |
| example)? |
| </h3> |
| <p> |
| |
| If your Java project is using source folders, then in the course of |
| compiling the source files in the project, the Java compiler copies |
| non-Java resources to the output folder as well so that they will be |
| available on the class path of the running program. To avoid certain |
| resources to be copied to the output location you can set a resource |
| filter in the Java compiler preferences: <strong>Window > Preferences |
| > Java > Compiler > Building</strong> |
| </p> |
| <h3> |
| How do I prevent having my documentation files from being copied to the |
| project's output folder? |
| </h3> |
| |
| <p> |
| Use source folders and put any resources that you do not want to be |
| copied to the output folder into a separate folder that is not included |
| on the class path. You can also set a resource filter in the Java |
| compiler preferences: <strong>Window > Preferences > Java > |
| Compiler > Building</strong> to for example *.doc. |
| </p> |
| |
| <h3> |
| How do I create a default package? |
| </h3> |
| <p> |
| You don't have to. Files in the root folder of a source folder or project |
| are considered to be in the default package. In effect, every source |
| folder has the capability of having a fragment of the default package. |
| </p> |
| <h3> |
| What is refactoring? |
| </h3> |
| <p> |
| |
| Refactoring means behavior-preserving program transformations. The JDT |
| supports a number of transformations described in Martin Fowler's book |
| <em>Refactoring: Improving the Design of Existing Code</em>, |
| Addison-Wisely 1999. |
| </p> |
| <h3> |
| When do I use Open Declaration (F3)? |
| </h3> |
| <p> |
| To find out the Java element that corresponds to the selected source |
| range with the help of the compiler. |
| </p> |
| <h3> |
| |
| Is the Java program information (type hierarchy, declarations, |
| references, for example) produced by the Java builder? Is it still |
| updated when auto-build is off? |
| </h3> |
| <p> |
| The Java program information is independent from the Java builder. It is |
| automatically updated when performing resource changes or Java |
| operations. In particular, all the functionality offered by the Java |
| tooling (for example, type hierarchies, code assisting, search) will |
| continue to perform accurately when auto-build is off; for example, when |
| doing heavy refactoring which require to turn off the builders, you can |
| still use code assist, which will reflect the latest changes (not yet |
| build). Other than the launching (that is, running and debugging) of |
| programs, the only functionality which requires the Java builder is the |
| evaluation of code snippets. |
| </p> |
| <h3> |
| After reopening a workbench, the first build that happens after editing a |
| Java source file seems to take a long time. Why is that? |
| </h3> |
| <p> |
| The Java incremental project builder saves its internal state to a file |
| when the workbench is closed. On the first build after the project is |
| reopened, the Java incremental project builder will restore its internal |
| state. When this file is large, the user experiences an unusually long |
| build delay. |
| </p> |
| |
| <h3> |
| I can't see a type hierarchy for my class. What can I do? |
| </h3> |
| <p> |
| Check that you have your build class path set up properly. Setting up the |
| proper build class path is an important task when doing Java development. |
| Without the correct build path, you will not be able to compile your |
| code. In addition, you will not be able to search or look at the type |
| hierarchies for Java elements. |
| </p> |
| <h3> |
| How do I turn off "auto compile" and do it manually when I want? |
| </h3> |
| <p> |
| |
| Clear the <strong>Build automatically</strong> checkbox on the <a class= |
| "command-link" href= |
| 'javascript:executeCommand("org.eclipse.ui.window.preferences(preferencePageId=org.eclipse.ui.preferencePages.Workspace)")'> |
| <img src="PLUGINS_ROOT/org.eclipse.help/command_link.svg" alt= |
| "Opens the Workspace preference page" /> <strong>General > |
| Workspace</strong></a> preference page. When you want to build, press |
| <kbd>Ctrl+B</kbd>, or select <strong>Project > Build All</strong> from |
| the menu bar. |
| </p> |
| |
| <p> |
| <b>Hint</b>: when you turn "auto compile" off and build manually, you may |
| also want to select the <strong>Save automatically before build</strong> |
| checkbox on the <a class="command-link" href= |
| 'javascript:executeCommand("org.eclipse.ui.window.preferences(preferencePageId=org.eclipse.ui.preferencePages.Workspace)")'> |
| <img src="PLUGINS_ROOT/org.eclipse.help/command_link.svg" alt= |
| "Opens the Workspace preference page" /> <strong>General > |
| Workspace</strong></a> preference page. |
| </p> |
| |
| <h3> |
| When I select a method or a field in the Outline view, only the source |
| for that element is shown in the editor. What do I do to see the source |
| of the whole file? |
| </h3> |
| <p> |
| There is a toolbar button <b>Show Source of Selected Element Only</b> - |
| all you have to do is un-press it. |
| </p> |
| <h3> |
| Can I nest source folders? |
| </h3> |
| |
| <p> |
| Yes, you can use exclusion filters to create nested source folders. |
| </p> |
| <h3> |
| Can I have separate output folders for each source folder? |
| </h3> |
| <p> |
| Yes, select the <b>Allow output folders for source folders</b> checkbox |
| in the <b>Java Build Path > Source</b> property page of your Java |
| project. |
| </p> |
| |
| <h3> |
| Can I have an output or source folder that is located outside of the |
| workspace? |
| </h3> |
| <p> |
| Yes, you can create a linked folder that points to the desired location |
| and use that folder as the source or output folder in your Java project. |
| </p> |
| |
| <h3 class="related">Related concepts</h3> |
| <a href="../concepts/concept-jdt.htm">Java development tools (JDT)</a> |
| |
| <h3 class="related">Related references</h3> |
| <a href="../reference/ref-properties-build-path.htm">Java build path |
| page</a><br /> |
| <a href="../reference/ref-jdt-glossary.htm">JDT glossary</a> |
| </body> |
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