CORE JAVA INTERVIEW QUESTIONS
201. What is the relationship between the
Canvas class and the Graphics class?
A Canvas object
provides access to a Graphics object via its paint() method.
202. What are the high-level thread states?
The
high-level thread states are ready, running, waiting, and dead.
203. What value does read() return when it
has reached the end of a file?
The read() method
returns -1 when it has reached the end of a file.
204. How are the elements of a BorderLayout
organized?
The elements
of a BorderLayout are organized at the borders (North, South,
East, and West) and the center of a container.
205. What is the difference between a Window
and a Frame?
The Frame class
extends Window to define a main application window that can
have a menu bar.
206. Can an object be garbage collected while
it is still reachable?
A reachable
object cannot be garbage collected. Only unreachable objects may be garbage
collected.
207. What is the difference between the
Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?
The Reader/Writer class
hierarchy is character-oriented, and the InputStream/OutputStream class hierarchy is byte-oriented.
208. How are the elements of a CardLayout
organized?
The elements
of a CardLayout are stacked, one on top of the other, like a
deck of cards.
209. What is the purpose of the File class?
The File class
is used to create objects that provide access to the files and directories of a local file system.
210. Can an exception be rethrown?
Yes, an
exception can be rethrown.
211. Which Math method is used to calculate
the absolute value of a number?
The abs() method
is used to calculate absolute values.
212. Which
class is the immediate superclass of the Container class?
Component.
213. How can the Checkbox class be used to
create a radio button?
By
associating Checkbox objects with a CheckboxGroup.
214. What happens when you invoke a thread's
interrupt method while it is sleeping or waiting?
When a
task's interrupt() method is executed, the task enters the ready
state. The next
time the task enters the running state, an InterruptedException is
thrown.
215. What is the difference between a Choice
and a List?
A Choice is
displayed in a compact form that requires you to pull it down to see the list
of available choices. Only one item may be selected from a Choice.
A List may
be displayed in such a way that several List items are visible. A List supports the selection of one or more List items.
216. What class of exceptions are generated
by the Java run-time system?
The Java
runtime system generates RuntimeException and Error exceptions.
217. What class allows you to read objects
directly from a stream?
The ObjectInputStream class
supports the reading of objects from input streams.
218. What Checkbox method allows you to tell
if a Checkbox is checked?
getState().
219. What is a compilation unit?
A
compilation unit is a Java source code file.
220. What interface is extended by AWT event
listeners?
All AWT
event listeners extend the java.util.EventListener interface.
221. How can a dead thread be restarted?
A dead
thread cannot be restarted.
222. What is a layout manager?
A layout
manager is an object that is used to organize components in a container.
223. What is JFC
JFC stands for Java Foundation Classes. The Java Foundation Classes (JFC) are a
set of Java class libraries provided as part of Java 2 Platform, Standard
Edition (J2SE) to support building graphics user interface (GUI) and graphics
functionality for client applications that will run on popular platforms such
as Microsoft Windows, Linux, and Mac OSX.
224. What is AWT?
AWT stands for Abstract Window Toolkit. AWT enables programmers to develop Java applications with GUI components, such as windows, and buttons. The Java
Virtual Machine (JVM) is responsible for translating the AWT calls into the
appropriate calls to the host operating system.
225. What are the differences
between Swing and AWT?
AWT is heavy-weight components, but Swing is light-weight components. AWT is OS dependent because it uses native components, But Swing components are OS independent. We can change the look and feel in Swing which is not possible in
AWT.
Swing takes less memory compared to AWT. For drawing AWT uses screen
rendering where Swing uses double buffering.
226. What are heavyweight
components?
A heavyweight component is one that is associated with its own native screen
resource
227. What is lightweight
component?
A lightweight component is one that "borrows" the screen resource of
an ancestor which means it has no native resource of its own -- so it's
"lighter".
228. What is an event?
Changing the state of an object is called an event.
229. What is an event handler?
An event handler is a part of a computer program created to tell the program
how to act in response to a specific event.
230. What is a layout manager?
A layout manager is an object that is used to organize components in a
container.
231. Which containers use a
border Layout as their default layout?
The window, Frame and Dialog classes use a border layout as their default
layout.
232. What is the preferred size
of a component?
The preferred size of a component is the minimum component size that will allow
the component to display normally.
233. What method is used to
specify a container's layout?
The setLayout method is used to specify a container's layout.
234. Which containers use a
FlowLayout as their default layout?
The Panel and Applet classes use the FlowLayout as their default layout.
235. Which method of the
Component class is used to set the position and size of a component?
SetBounds