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
.Why 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 Observer 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
deprecated 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 FlowLayout 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.
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 ordered collections
of objects.
16. How does Java handle integer overflows and
underflows?
It uses those low order bytes 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 be 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 Collection.
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 using 8, 16, and 18 bit patterns. UTF-16 uses 16bit
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.
24. Which java.util classes and interfaces
support event handling?
The EventObject class and the EventListener interface
support event processing.
25. Is sizeof a keyword?
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 guarantee that a program will
not run out of memory. It is possible for programs to use up memory resources
faster than they are 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 package statement within a source code 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 predefined
slice of time and then reenters the pool of ready tasks. The scheduler then
determines which task should execute next, based on priority and other factors..
32. Name three Component subclasses that
support painting.
The Canvas, Frame, Panel, 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
35. What is clipping?
Clipping is the process of confining paint 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 are 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 checked exception may be thrown within the body of a
method, the method must either catch the exception or declare it in its throws
clause.
42. What is the difference between a MenuItem
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
scheduler 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, what
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
.
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.event 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 processing 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 expression involving the Boolean & operator 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 operands. If the first operand evaluates to false, 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 GregorianCalendar class?
The GregorianCalendar provides support for traditional
Western calendars.
57. Which Container method is used to cause a
container to be laid out and redisplayed?
validate()
58. What is the purpose of the Runtime class?
The purpose of the Runtime class is to provide access to the
Java runtime system.
59. How many times may an object's finalize()
method be invoked by the garbage
collector?
An object's finalize() method may only be invoked once by
the garbage collector.
60. What is the purpose of the finally clause
of a try-catch-finally statement?
The finally clause is used to provide the capability to
execute code no matter whether or not an exception is thrown or caught.
61. What is the argument type of a program's
main() method?
A program's main() method takes an argument of the String[]
type.
62. Which Java operator is right associative?
The =
operator is right associative.
63. What is the Locale class?
The Locale class is used to tailor program output to the
conventions of a particular geographic, political, or cultural region.
64. Can a double value be cast to a byte?
Yes, a double value can be cast to a byte.