| 16 |
Q |
What is the difference between invokeAndWait() and
invokeLater()? |
| |
A |
invokeAndWait is synchronous. It blocks until Runnable task is complete.
InvokeLater is asynchronous. It posts an action event to the
event queue and returns immediately. It will not wait for
the task to complete |
| |
|
|
| 17 |
Q |
Why should any swing call back implementation execute quickly? |
| |
A |
Callbacks are invoked by
the event dispatch thread. Event dispatch thread blocks processing
of other events as long as call back method executes. |
| |
|
|
| 18 |
Q |
What is an applet? |
| |
A |
Applet is a java program that runs
inside a web browser. |
| |
|
|
| 19 |
Q |
What is the difference between
applications and applets? |
| |
A |
Application must be run explicitly within Java Virtual
Machine whereas applet loads and
runs itself automatically in a java-enabled browser.
Application starts execution with its main method whereas
applet starts execution with its init method. Application
can run with or without graphical user interface whereas
applet must run within a graphical user interface. In order
to run an applet we need a java enabled web browser or an
appletviewer. |
| |
|
|
| 20 |
Q |
Which method is used by the applet
to recognize the
height and width? |
| |
A |
getParameters(). |
| |
|
|
| 21 |
Q |
When we should go for codebase in applet? |
| |
A |
If the applet class is not
in the same directory, codebase is used. |
| |
|
|
| 22 |
Q |
What is the lifecycle of an applet? |
| |
A |
init( ) method - called when an
applet is first loaded
start( ) method - called each time an applet is started
paint( ) method - called when the applet is minimized or
maximized
stop( ) method - called when the browser moves off the
applet's page
destroy( ) method - called when the browser is finished with
the applet |
| |
|
|
| 23 |
Q |
Which method is used for setting
security in applets? |
| |
A |
setSecurityManager |
| |
|
|
| 24 |
Q |
What is an event and what are the
models available for event handling? |
| |
A |
Changing the state of an object is called an event. An event is an event object that
describes a state of change. In other words,
event occurs when an action is generated, like pressing
a key on keyboard, clicking mouse, etc. There different types of models for handling events are event-inheritance
model and event-delegation model
|
| |
|
|
| 25 |
Q |
What are the advantages of the
event-delegation model over the event-inheritance model? |
| |
A |
Event-delegation model has two
advantages over event-inheritance model.
a)Event delegation model enables event handling by objects other than the ones
that generate the events. This allows a clean separation
between a component's design and its use.
b)It performs much better in applications where many events
are generated. This performance improvement is due to event-delegation model does not have to be
repeatedly process unhandled events as is the case of the
event-inheritance. |
| |
|
|
| 26 |
Q |
What is source and listener ? |
| |
A |
A source is an object that
generates an event. This occurs when the internal state of
that object changes in some way. A listener is an object
that is notified when an event occurs. It has two major
requirements. First, it must have been registered with a source to receive notifications about specific
event. Second, it must implement necessary methods to
receive and process these notifications. |
| |
|
|
| 27 |
Q |
What is controls and what
are different types of controls in AWT? |
| |
A |
Controls are components that allow
a user to interact with your application. AWT
supports the following types of controls: Labels, Push
Buttons, Check Boxes, Choice Lists, Lists, Scrollbars, Text
Components. These controls are subclasses of Component. |
| |
|
|
| 28 |
Q |
What is the difference between
choice and list? |
| |
A |
A Choice is displayed in a compact
form that requires you to pull it down to see the list of
available choices and only one item may be selected from a
choice. A List may be displayed in such a way that several
list items are visible and it supports the selection of one
or more list items. |
| |
|
|
| 29 |
Q |
What is the difference between
scrollbar and scrollpane? |
| |
A |
A Scrollbar is a Component, but not
a Container whereas Scrollpane is a Container and handles
its own events and perform its own scrolling. |
| |
|
|
| 30 |
Q |
What is a layout manager and what
are different types of layout managers available? |
| |
A |
A layout manager is an object that
is used to organize components in a container. The different
layouts are available are FlowLayout, BorderLayout,
CardLayout, GridLayout , GridBagLayout, Boxlayout and
SpringLayout |
| |
|
|
