questions-interviews.com

Interview Questions and Answers, Frequently Asked Questions (FAQs) and Useful Articles

Home  >> Interview Questions and Answers  >> Java Programming  >> Eclipse Interview Questions and Answers

Interview Questions & Answers


Eclipse Interview Questions and Answers


This page contains the collection of Eclipse Interview Questions and Answers / Frequently Asked Questions (FAQs) under category Java Programming. These questions are collected from various resources like informative websites, forums, blogs, discussion boards including MSDN and Wikipedia. These listed questions can surely help in preparing for Eclipse interview or job.

When does a plugin get started?

What are extensions and extension points?

How to access UI objects from a non-ui thread?

How to fire a key event in my test code to make the program act as if a user pressed a key?

Why do I get the error "org.eclipse.swt.SWTException: Invalid thread access"?

How to config a plugin to start automatically during platform starts up?

What is the classpath of a plug-in?

Do we need to explicitly invoke org.eclipse.swt.graphics.Image.dispose()?

What is Display, what is Shell?

How to resize my shell to get my changed widgets to lay out again?

Is there a built-in facility to check whether a given value is valid compared to the effective facets of its type?

How can I change the window icon in my application?

What is optional dependency?

What is EMF?

What is included in the Rich Client Platform?

What are the differences between Require-Bundle and Import-Package?

Top     

When does a plugin get started?
Each plug-in can be viewed as having a declarative section and a code section. The declarative part is contained in the plugin.xml file. This file is loaded into a registry when the platform starts up and so is always available, regardless of whether a plug-in has started. The code section are laze loaded by default. They are activated only when their functionality has been explicitly invoked by the user.

What are extensions and extension points?
Loose coupling in Eclipse is achieved partially through the mechanism of extensions and extension points. When a plug-in wants to allow other plug-ins to extend or customize portions of its functionality, it will declare an extension point. The extension point declares a typically a combination of XML markup and Java interfaces, that extensions must conform to. Plug-ins that want to connect to that extension point must implement that contract in their extension.

How to access UI objects from a non-ui thread?
Use Display.getDefault().asyncExec(new Runnable()...) Display.asyncExec causes the run() method of the runnable to be invoked by the user-interface thread at the next reasonable opportunity. The caller of this method continues to run in parallel, and is not notified when the runnable has completed.

How to fire a key event in my test code to make the program act as if a user pressed a key?
Two ways to implement it in code: generating OS level key event use Display.post(Event) or use Widge.notifyListeners(...) to just notify a widget's listeners.

Why do I get the error "org.eclipse.swt.SWTException: Invalid thread access"?
SWT implements a single-threaded UI model often called apartment threading. In this model, only the UI-thread can invoke UI operations. SWT strictly enforces this rule. If you try and access an SWT object from outside the UI-thread, you get the exception "org.eclipse.swt.SWTException: Invalid thread access". The following code sets the text of a label from a background thread and waits for the operation to complete: display.syncExec( new Runnable() { public void run(){ label.setText(text); } });

How to config a plugin to start automatically during platform starts up?
Define the 'Eclipse-AutoStart=true' header in Manifest file.

What is the classpath of a plug-in?
The OSGi parent class loader. (Java boot class loader by default); The exported libraries of all imported plug-ins; The declared libraries of the plug-in and all its fragments.

Do we need to explicitly invoke org.eclipse.swt.graphics.Image.dispose()?
Application code must explicitly invoke the Image.dispose() method to release the operating system resources managed by each instance when those instances are no longer required. This is because that the Java finalization is too weak to reliably support management of operating system resources.

What is Display, what is Shell?
The Display class respresents the GUI process(thread), the Shell class represents windows.

How to resize my shell to get my changed widgets to lay out again?
A layout is only performed automatically on a Composite's children when the Composite is resized, including when it is initially shown. To make a Composite lay out its children under any other circumstances, such as when children are created or disposed, its layout() method must be called.

Is there a built-in facility to check whether a given value is valid compared to the effective facets of its type?
To determine if a literal is valid with respect to a simple type, you can use either XSDSimpleTypeDefinition.isValidLiteral or XSDSimpleTypeDefinition.assess.

How can I change the window icon in my application?
Define a product via the products extension point and specify the windowImages property to refer to two image files, a 16x16 one and a 32x32 one.

What is optional dependency?
plug-in prerequisite elements can be made optional by adding the optional="true" attribute in Manifest file(see below for an example). Marking an import as optional simply states that if the specified plug-in is not found at runtime, the dependent plug-in should be left enabled. This is used when a plug-in can be used in many scenarios or it is reasonable to operate with reduced function. It allows the creation of minimal installs that cover functional subsets. Require-Bundle: org.eclipse.swt; optional="true"

What is EMF?
The Eclipse Modeling Framework is a Java/XML framework for generating tools and other applications based on simple class models. EMF helps you rapidly turn models into efficient, correct, and easily customizable Java code. It is intended to provide the benefits of formal modeling, but with a very low cost of entry. In addition to code generation, it provides the ability to save objects as XML documents for interchange with other tools and applications.

What is included in the Rich Client Platform?
Eclipse Runtime, SWt, JFace, Workbench

What are the differences between Require-Bundle and Import-Package?
There are two complementary ways of depending on something from outside a given plug-in; Require-Bundle and Import-Package.

Top     

Our Keywords and Tags:
free eclipse interview questions