Interview Questions

2009-11-05T03:20:00.001-08:00

47. What is the range of the short type?
The range of the short type is -(2^15) to 2^15 - 1.
48. What is the range of the char type?
The range of the char type is 0 to 2^16 - 1.
49. In which package are most of the AWT events that support the event-delegation
model defined?
Most of the AWT-related events of the event-delegation model are defined in the
java.awt.ev ent package. The AWTEvent class is defined in the java.awt package.
50. What is the immediate superclass of Menu?
MenuItem
51. What is the purpose of finalization?
The purpose of finalization is to give an unreachable object the opportunity to perform
any cleanup p rocessing before the object is garbage collected.
52. Which class is the immediate superclass of the MenuComponent class.
Object
53. What invokes a thread's run() method?
After a thread is started, via its start() method or that of the Thread class, the JVM
invokes the thread's run() method when the thread is initially executed.
54. What is the difference between the Boolean & operator and the && operator?
If an ex pression involving the Boolean & o perator is evaluated, both operands are
evaluated. Then the & operator is applied to the operand. When an expression involving
the && operator is evaluated, the first operand is evaluated. If the first operand returns a
value of true then the second operand is evaluated. The && operator is then applied to
the first and second op erands. If the first operand evaluates to f alse, the evaluation of the
second operand is skipped.
55. Name three subclasses of the Component class.
Box.Filler, Button, Canvas, Checkbox, Choice, Container, Label, List, Scrollbar, or
TextComponent
56. What is the Grego rianCalendar class?
The Grego rianCalendar provides support for traditional Western calendars.
57. Which Container method is used to cause a container to be laid out and redisplayed?
validate()

2009-11-05T03:19:00.000-08:00

35. What is clipping?
Clipping is the process of confining p aint operations to a limited area or shape.
36. What is a native method?
A native method is a method that is implemented in a language other than Java.
37. Can a for statement loop indefinitely?
Yes, a for statement can loop indefinitely. For example, consider the following:
for(;;) ;
38. What are order of precedence and associativity, and how ar e they used?
Order of precedence determines the order in which operators are evaluated in
expressions. Associatity determines whether an expression is evaluated left-to-right or
right-to-left
39. When a thread blocks on I/O, what state does it enter?
A thread enters the waiting state when it blocks on I/O.
40. To what value is a variable of the String type automatically initialized?
The default value of an String type is null.
41. What is the catch or declare rule for method declarations?
If a ch ecked exception may be thrown within the body of a method, the method must
either catch the ex ception or declare it in its throws clause.
42. What is the difference between a Menu Item and a CheckboxMenuItem?
The CheckboxMenuItem class extends the MenuItem class to support a menu item that
may be checked or unchecked.
43. What is a task's priority and how is it used in scheduling?
A task's priority is an integer value that identifies the relative order in which it should be
executed with respect to other tasks. The sch eduler attempts to schedule higher priority
tasks before lower priority tasks.
44. What class is the top of the AWT event hierarchy?
The java.awt.AWTEvent class is the highest-level class in the AWT event-class
hierarchy.
45. When a thread is created and started, wh at is its initial state?
A thread is in the ready state after it has been created and started.
46. Can an anonymous class be declared as implementing an interface and extending a
class?
An anonymous class may implement an interface or extend a superclass, but may not be
declared to do both.

2009-11-05T03:18:00.000-08:00

24. Which java.util classes and interfaces support event handling?
The EventObject class and the EventListener interface support event processing.
25. Is sizeof a k eyword?
The sizeof operator is not a keyword.
26. What are wrapped classes?
Wrapped classes are classes that allow primitive types to be accessed as objects.
27. Does garbage collection guarantee that a program will not run out of memory?
Garbage collection does not guar antee that a program will not run out of memory. It is
possible for programs to use up memory resources faster than they ar e garbage collected.
It is also possible for programs to create objects that are not subject to garbage collection
28. What restrictions are placed on the location of a pack age statement
within a source cod e file?
A package statement must appear as the first line in a source code file (excluding blank
lines and comments).
29. Can an object's finalize() method be invoked while it is reachable?
An object's finalize() method cannot be invoked by the garbage collector while the object
is still reachable. However, an object's finalize() method may be invoked by other
objects.
30. What is the immediate superclass of the Applet class?
Panel
31. What is the difference between preemptive scheduling and time slicing?
Under preemptive scheduling, the highest priority task executes until it enters the waiting
or dead states or a higher priority task comes into existence. Under time slicing, a task
executes for a p redefined slice of time and then reenters the pool of ready tasks. The
scheduler then d etermines which task should execute next, based on priority and
other factors.
32. Name three Component subclasses that support painting.
The Canvas, Frame, Pan el, and Applet classes support painting.
33. What value does readLine() return when it has reached the end of a file?
The readLine() method returns null when it has reached the end of a file.
34. What is the immediate superclass of the Dialog class?
Window

Core Java Interview Question

2009-11-05T01:54:00.000-08:00

13. What is the Collections API?
The Collections API is a set of classes and interfaces that support operations on
collections of objects.

14. Which characters may be used as the second character of an identifier,
but not as the first character of an identifier?
The digits 0 through 9 may not be used as the first character of an identifier but they may
be used after the first character of an identifier.

15. What is the List interface?
The List interface provides support for ord ered collections of objects.

16. How does Java handle integer overflows and underflows?
It uses those low order b ytes of the result that can fit into the size of the type allowed by
the operation.

17. What is the Vector class?
The Vector class provides the capability to implement a growable array of objects

18. What modifiers may be used with an inner class that is a member of an outer class?
A (non-local) inner class may b e declared as public, protected, private, static, final, or
abstract.

19. What is an Iterator interface?
The Iterator interface is used to step through the elements of a C ollection.

20. What is the difference between the >> and >>> operators?
The >> operator carries the sign bit when shifting right. The >>> zero-fills bits that have
been shifted out.

21. Which method of the Component class is used to set the position and
size of a component?
setBounds()

22. How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8
characters?
Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character set uses
only 7 bits, it is usually represented as 8 bits. UTF-8 represents characters u sing 8, 16,
and 18 bit patterns. UTF-16 uses 16-bit and larger bit patterns.

23What is the difference between yielding and sleeping?
When a task invokes its yield() method, it returns to the ready state. When a task invokes
its sleep() method, it returns to the waiting state.

Core Java Interview Questions

2009-11-05T01:10:00.000-08:00

CORE JAVA INTERVIEW QUESTIONS AND ANSWERS

1.what is a transient variable?

A transient variable is a variable that may not be serialized.

2.which containers use a border Layout as their default layout?

The window, Frame and Dialog classes use a border layout as their default layout.

3.Wh y do threads block on I/O?

Threads block on i/o (that is enters the waiting state) so that other threads may execute

while the i/o Operation is performed.

4. How are Observ er and Observable used?

Objects that subclass the Observable class maintain a list of observers. When an

Observable object is updated it invokes the update() method of each of its observers to

notify the observers that it has changed state. The Observer interface is implemented by

objects that observe Observable objects.

5. What is synchronization and why is it important?

With respect to multithreading, synchronization is the capability to control the access of

multiple threads to shared resources. Without synchronization, it is possible for one

thread to modify a shared object while another thread is in the process of using or

updating that object's value. This often leads to significant errors.

6. Can a lock be acquired on a class?

Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object..

7. What's new with the stop(), suspend() and resume() methods in JDK 1.2?

The stop(), suspend() and resume() methods have been depr ecated in JDK 1.2.

8. Is null a keyword?

The null value is not a keyword.

9. 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.

10. What method is used to specify a container's layout?

The setLayout() method is used to specify a container's layout.

11. Which containers use a FlowLayout as their default layout?

The Panel and Applet classes use the FlowLayo ut as their default layout.

12. What state does a thread enter when it terminates its processing?

When a thread terminates its processing, it enters the dead state.