Interview Questions.

Question 1. When Does A Plugin Get Started?

Answer :

Each plug-in may be considered as having a declarative segment and a code section. The declarative component is contained inside the plugin.Xml record. This file is loaded into a registry whilst the platform starts offevolved up and so is always to be had, irrespective of whether a plug-in has began. The code segment are laze loaded by means of default. They are activated handiest whilst their capability has been explicitly invoked through the consumer.

Question 2. What Are Extensions And Extension Points?

Answer :

Loose coupling in Eclipse is executed partially via the mechanism of extensions and extension factors. When a plug-in wants to permit different plug-ins to extend or customise quantities of its functionality, it'll claim an extension point. The extension point proclaims a usually a mixture of XML markup and Java interfaces, that extensions must conform to. Plug-ins that want to connect to that extension point must put into effect that contract in their extension.

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Question 3. How To Access Ui Objects From A Non-ui Thread?

Answer :

Use Display.GetDefault().AsyncExec(new Runnable()…) Display.AsyncExec causes the run() technique of the runnable to be invoked by using the user-interface thread at the subsequent affordable possibility. The caller of this method continues to run in parallel, and is not notified when the runnable has completed.

Question four. How To Fire A Key Event In My Test Code To Make The Program Act As If A User Pressed A Key?

Answer :

Two approaches to enforce it in code: producing OS stage key event use Display.Post(Event) or use Widge.NotifyListeners(…) to just notify a widget’s listeners.

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Question five. Why Do I Get The Error “org.Eclipse.Swt.Swtexception: Invalid Thread Access”?

Answer :

SWT implements a unmarried-threaded UI model often referred to as condo threading. In this model, best the UI-thread can invoke UI operations. SWT strictly enforces this rule. If you try and get right of entry to an SWT item from outside the UI-thread, you get the exception “org.Eclipse.Swt.SWTException: Invalid thread get right of entry to”.

The following code units the textual content of a label from a historical past thread and waits for the operation to complete:

show.SyncExec( new Runnable()

public void run() label.SetText(text);

);

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Question 6. How To Config A Plugin To Start Automatically During Platform Starts Up?

Answer :

Define the ‘Eclipse-AutoStart=authentic’ header in Manifest report.

Question 7. What Is The Classpath Of A Plug-in?

Answer :

The OSGi discern magnificence loader. (Java boot elegance loader by way of default); The exported libraries of all imported plug-ins; The declared libraries of the plug-in and all its fragments.

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Question 8. Do We Need To Explicitly Invoke Org.Eclipse.Swt.Pics.Photograph.Dispose()?

Answer :

Application code should explicitly invoke the Image.Dispose() approach to launch the working machine resources controlled by way of every instance while the ones times are not required. This is due to the fact that the Java finalization is too susceptible to reliably help management of running machine resources.

Question nine. What Is Display, What Is Shell?

Answer :

The Display elegance respresents the GUI method(thread), the Shell magnificence represents windows.

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Question 10. How To Resize My Shell To Get My Changed Widgets To Lay Out Again?

Answer :

A format is most effective performed automatically on a Composite’s kids whilst the Composite is resized, inclusive of whilst it is to start with proven. To make a Composite lay out its children below some other circumstances, consisting of whilst youngsters are created or disposed, its format() technique should be known as.

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Question eleven. Is There A Built-in Facility To Check Whether A Given Value Is Valid Compared To The Effective Facets Of Its Type?

Answer :

To determine if a literal is valid with recognize to a easy kind, you can use both XSDSimpleTypeDefinition.IsValidLiteral or XSDSimpleTypeDefinition.Determine.

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Question 12. How Can I Change The Window Icon In My Application?

Answer :

Define a product thru the goods extension point and specify the windowImages assets to refer to  picture documents, a sixteen×16 one and a 32×32 one.

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Question thirteen. What Is Optional Dependency?

Answer :

plug-in prerequisite factors can be made non-obligatory with the aid of adding the non-obligatory=”true” attribute in Manifest report(see beneath for an example). Marking an import as non-compulsory actually states that if the specified plug-in isn't always discovered at runtime, the established plug-in must be left enabled. This is used while a plug-in can be used in many situations or it is reasonable to function with reduced characteristic. It lets in the introduction of minimum installs that cover useful subsets. Require-Bundle: org.Eclipse.Swt; elective=”authentic”

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Question 14. What Is Emf?

Answer :

The Eclipse Modeling Framework is a Java/XML framework for producing tools and different packages based totally on easy class models. EMF allows you rapidly flip fashions into efficient, correct, and without difficulty customizable Java code. It is intended to offer the blessings of formal modeling, however with a completely low cost of entry. In addition to code technology, it presents the capability to save gadgets as XML files for interchange with different gear and packages.

Question 15. What Is Included In The Rich Client Platform?

Answer :

Eclipse Runtime, SWt, JFace, Workbench.

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Question 16. What Is An Ide?

Answer :

An IDE or Integrated Development Environment is a software program program this is designed to help programmers and developers construct software.

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Question 17. What Are The Basic Things An Ide Includes?

Answer :

Most IDEs encompass:

1. A source code editor
2. A compiler and/or an interpreter
3. Build automation equipment
4. A debugger

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Question 18. What Is Eclipse?

Answer :

Eclipse is an open source network whose tasks are centered on constructing an extensible development platform, runtimes and alertness frameworks for building, deploying and coping with software throughout the entire software program lifecycle.

Eclipse is used in several distinctive regions, e.G. As a improvement surroundings for Java or Android programs.

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Question 19. Who Governs The Eclipse Projects?

Answer :

The Eclipse tasks are ruled by way of the Eclipse Foundation. The Eclipse Foundation is a non-profit, member supported employer that hosts the Eclipse Open Source tasks.

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Question 20. What Is Rich Client Platform?

Answer :

The minimum set of plugins had to construct a rich consumer utility is together known as the Rich Client Platform. It approach your application need best require two plugins, org.Eclipse.Ui and org.Eclipse.Center.Runtime, and their conditions.

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Question 21. What Are The Prerequisite For Installing Eclipse?

Answer :

Eclipse calls for an mounted Java runtime. You might also both install a Java Runtime Environment (JRE), or a Java Development Kit (JDK), depending on what you need to do with Eclipse. If you propose to use Eclipse for Java development, you then need to deploy a JDK. If you aren’t making plans to use Eclipse for Java improvement and need to shop a few disk space, deploy a JRE.

Question 22. What Is A Workspace?

Answer :

The workspace is the bodily vicinity (record course) you are operating in. Your tasks, source documents, pics and different artifacts can be stored and stored in your workspace. The workspace also contains options settings, plugin precise meta data, logs and many others

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Question 23. What Is An Eclipse Project?

Answer :

An Eclipse assignment incorporates:

1. Supply
2. Configuration and
three. Binary files related to a certain undertaking

Eclipse corporations the above into buildable and reusable devices. An Eclipse project could have natures assigned to it which describe the reason of this undertaking. For example the Java nature defines a assignment as Java task. Projects will have multiple natures combined to model specific technical factors.

Natures for a assignment are defined via the .Undertaking document within the venture directory.

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Question 24. What Are Visible Parts Or User Interface Components Of An Eclipse Window?

Answer :

The most important seen elements of an eclipse window are:

1. Views
2. Editors (all seem in one editor location)
3. Menu Bar
four. Toolbar

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Question 25. What Are Views?

Answer :

A view is normally used to work on a fixed of statistics, which is probably a hierarchical structure. If records is changed through the view, the exchange is at once applied to the underlying facts structure. A view once in a while allows us to open an editor for a selected set of information.

E.G.:Package Explorer is a view, which lets in you to browse the files of Eclipse initiatives.

Question 26. What Are Editors?

Answer :

Editors are commonly used to regulate a unmarried facts detail, e.G. A file or a facts object.

Question 27. What Is Difference Between Views And Editors?

Answer :

Editors are used to edit the challenge facts and Views are used to view the undertaking metadata. For example the package deal explorer indicates the java documents in the assignment and the java editor is used to edit a java file.

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Question 28. What Is A Perspective?

Answer :

An eclipse angle is the call given to an preliminary collection and arrangement of views and an editor vicinity. The default perspective is referred to as java.

Question 29. What Is Refactoring And How Is Refactoring In Eclipse Done?

Answer :

Refactoring is the method of restructuring the code with out converting its conduct.

For instance renaming a Java elegance or approach is a refactoring interest.

Eclipse supports several refactoring sports, as an instance renaming or transferring.

E.G.:To use the Rename refactoring, you could right-click on to your elegance (in the editor or Package Explorer) and choose Refactor ? Rename to rename your magnificence. Eclipse will make certain that all calls to your Workspace on your class or approach are renamed.

Question 30. Where Do You Set The Memory Heap Size In Eclipse?

Answer :

Eclipse set up consists of a record known as eclipse.Ini which permits you to configure the memory parameters for the Java virtual device which runs the Eclipse IDE. For example the -Xmx parameter may be used to define how big the Java heap length can get. -Xms defines the preliminary heap size of the Java digital device

Question 31. Why Should We Close A Project In Eclipse?

Answer :

An eclipse workspace can include any number of projects. A undertaking can be both within the open country or closed kingdom.

Open tasks:

Consume reminiscence:

Take up build time specifically when the Clean All Projects (Project > Clean all initiatives) with the Start a construct at once option is used.

A closed undertaking is seen in the Package Explorer view but its contents can't be edited the usage of the Eclipse consumer interface.

Question 32. What Are Extensions And Extension Points In Eclipse?

Answer :

Loose coupling in Eclipse is finished partly thru the mechanism of extensions and extension points. A trendy example for this would be: electrical outlets. The outlet, or socket, is the extension factor; the plug, or mild bulb that connects to it, is the extension. As with electric stores, extension factors are available in a wide variety of shapes and sizes, and most effective the extensions which can be designed for that unique extension point will fit.

When a plugin desires to permit different plugins to extend or personalize quantities of its functionality, it'll declare an extension point. The extension factor pronounces typically a combination of XML markup and Java interfaces. The extensions should comply with this. Plugins that need to connect to that extension point need to implement that contract in their extension. Extension points are outline inside the plugin.Xml

Question 33. What Are Eclipse Plugins?

Answer :

A software thing in Eclipse is called a plugin. The Eclipse IDE allows the developer to extend the IDE capability via plugins. For instance you could create new menu entries and related actions thru plugins.

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Question 34. Does Eclipse Save Any Report Or Log File?

Answer :

Yes, every time it encounters a trouble that doesn't warrant launching a dialog, Eclipse saves a report inside the workspace log record. You can find the log file at :workspace/.Metadata/.Log.

Question 35. What Is “cannot Find A Vm” Start Up Problem In Eclipse?

Answer :

Eclipse requires a JVM to run and does now not encompass one in the download. You may additionally have a VM, but Eclipse cannot find it. To avoid feasible conflicts, continually specify the VM you're the usage of with the -vm command-line argument.

Question 36. What Is “disk Full Or Out Of Memory” Problem?

Answer :

Eclipse, specially 2.1 and in advance, does no longer constantly gracefully document disk-full mistakes or out-of-memory errors. Make sure that you have adequate disk space and which you are giving the Java VM enough heap area.

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Question 37. How To Install New Plugins?

Answer :

Best approach is to apply the Eclipse Update Manager. The Update Manager lets in you to discover new plugins in your gadget, your network, or the Internet, compare new plugins on your configuration, and set up handiest those that are well matched with your modern configuration. The Update Manager is invoked through Help > Software Updates.

Question 38. How To Remove A Plugin?

Answer :

plugins from Eclipse need to in no way be removed. Instead they can be disabled through the usage of the Eclipse Update Manager.

Run Help > About Eclipse >Installation Details, choose the software program you not want and click Uninstall.

Question 39. Where Does System.Out And System.Err Output Logged?

Answer :

Eclipse is genuinely a Java program and whilst launched from a shell or command line, the output will generally move returned to that shell. In Windows, the output will disappear completely if Eclipse is released the usage of the javaw.Exe VM. As output is misplaced, it’s higher to log blunders facts with the aid of using the platform logging facility.

Question forty. What Is Autobuilding Of Java Code In Eclipse?

Answer :

Eclipse affords autobuild facilities. If a resource changes, the platform tests the assignment description file ( .Project in your projects). When the record carries a reference to the Java builder, the builder gets notified of the change and will then collect the Java supply file and it’s dependents.

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Question forty one. What Is A Quick Fix?

Answer :

As you type characters into an eclipse editor it analyzes the record content for capability errors and warnings. The java editor uses the java syntax to stumble on mistakes in the code. When it finds mistakes it highlights errors the usage of crimson wavy lines below the offending code and a marker in the left editor margin.

The marker may be decided on with the left mouse to set off the Quick Fix pop-up dialog. It affords a list of feasible corrections for the mistake.

Question 42. What Is Hot Code Replace?

Answer :

Hot code enables you to alternate code even as debugging. It truely means that you could exchange the code in debug mode and see its have an effect on.

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Question 43. Why Does The Eclipse Compiler Create A Different Serialversionuid From Javac?

Answer :

Serializable classes compiled with Eclipse are not like minded with the same training compiled the usage of javac. When training compiled in Eclipse are written to an object stream, you may no longer be capable of examine them back in a program that was compiled somewhere else. Many human beings blame this on the Eclipse compiler, assuming that it's far one way or the other no longer conforming nicely to spec. In truth, this may be a problem among any  compilers or maybe  versions of a compiler provided with the aid of the identical dealer.

If you need object serialization, the most effective way to be safe is to explicitly outline the serialVersionUID in your code:

class MyClass implements Serializable 

public static final long serialVersionUID = 1;

on every occasion your magnificence adjustments say it's miles incompatible with previously serialized variations, virtually increment this number.

Question forty four. What Is The Difference Between A Perspective And A Workbench Page?

Answer :

The workbench web page is the main body of a workbench window: among the toolbar and the reputation line, the place that consists of views and editors.
The workbench page can have one or more views associated with it that outline the layout of the views and editors in the web page.