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1000 Interview Questions on Java / J2EE technologies. Buy now for JUST 12.99 USD or 400 INR.
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Java Interview Questions
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Java, the language, is a high-level object-oriented programming language, influenced in various ways by C, C++, and Smalltalk, with ideas borrowed from other languages as well (see O'Reilly's History of Programming Languages). Its syntax was designed to be familiar to those familiar with C-descended "curly brace" languages, but with arguably stronger OO principles than those found in C++, static typing of objects, and a fairly rigid system of exceptions that require every method in the call stack to either handle exceptions or declare their ability to throw them. Garbage collection is assumed, sparing the developer from having to free memory used by obsolete objects.
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Java FAQs - 1 |
Java FAQs - 2 |
Java FAQs - 3 |
Java FAQs - 4 |
Java FAQs - 5
Java FAQs - 6 |
Java FAQs - 7 |
Java FAQs - 8 |
Java FAQs - 9 |
Java FAQs - 10
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Core Java Interview Questions - Part8
126. How does multithreading take place on a computer with a single CPU?
The operating system's task scheduler allocates execution time to multiple
tasks. By
quickly switching between executing tasks, it creates the impression that tasks
execute
sequentially.
127. When does the compiler supply a default constructor for a class?
The compiler supplies a default constructor for a class if no other constructors
are
provided.
128. When is the finally clause of a try-catch-finally statement executed?
The finally clause of the try-catch-finally statement is always executed unless
the thread
of execution terminates or an exception occurs within the execution of the
finally clause.
129. Which class is the immediate superclass of the Container class?
Component
130. If a method is declared as protected, where may the method be accessed?
A protected method may only be accessed by classes or interfaces of the same
package or
by subclasses of the class in which it is declared.
131. How can the Checkbox class be used to create a radio button?
By associating Checkbox objects with a CheckboxGroup.
132. Which non-Unicode letter characters may be used as the first character
of an identifier?
The non-Unicode letter characters $ and _ may appear as the first character of
an
identifier
133. What restrictions are placed on method overloading?
Two methods may not have the same name and argument list but different return
types.
134. 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.
135. What is casting?
There are two types of casting, casting between primitive numeric types and
casting
between object references. Casting between numeric types is used to convert
larger
values, such as double values, to smaller values, such as byte values. Casting
between
object references is used to refer to an object by a compatible class,
interface, or array
type reference.
136. What is the return type of a program's main() method?
A program's main() method has a void return type.
137. Name four Container classes.
Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane
138. 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.
139. What class of exceptions are generated by the Java run-time system?
The Java runtime system generates RuntimeException and Error exceptions.
140. What class allows you to read objects directly from a stream?
The ObjectInputStream class supports the reading of objects from input streams.
141. What is the difference between a field variable and a local variable?
A field variable is a variable that is declared as a member of a class. A local
variable is a
variable that is declared local to a method.
142. Under what conditions is an object's finalize() method invoked by the
garbage
collector?
The garbage collector invokes an object's finalize() method when it detects that
the object
has become unreachable.
143. How are this() and super() used with constructors?
this() is used to invoke a constructor of the same class. super() is used to
invoke a
superclass constructor.
144. What is the relationship between a method's throws clause and the
exceptions
that can be thrown during the method's execution?
A method's throws clause must declare any checked exceptions that are not caught
within
the body of the method.
145. What is the difference between the JDK 1.02 event model and the
event-delegation
model introduced with JDK 1.1?
The JDK 1.02 event model uses an event inheritance or bubbling approach. In this
model,
components are required to handle their own events. If they do not handle a
particular
event, the event is inherited by (or bubbled up to) the component's container.
The
container then either handles the event or it is bubbled up to its container and
so on, until
the highest-level container has been tried..
In the event-delegation model, specific objects are designated as event handlers
for GUI
components. These objects implement event-listener interfaces. The
event-delegation
model is more efficient than the event-inheritance model because it eliminates
the
processing required to support the bubbling of unhandled events.
146. How is it possible for two String objects with identical values not to be
equal
under the == operator?
The == operator compares two objects to determine if they are the same object in
memory. It is possible for two String objects to have the same value, but
located
indifferent areas of memory.
147. Why are the methods of the Math class static?
So they can be invoked as if they are a mathematical code library.
148. What Checkbox method allows you to tell if a Checkbox is checked?
getState()
149. What state is a thread in when it is executing?
An executing thread is in the running state.
150. What are the legal operands of the instanceof operator?
The left operand is an object reference or null value and the right operand is a
class,
interface, or array type.
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