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 displaynormally.
the component to displaynormally.
10. What method is used to specify a container's layout?
ThesetLayout 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.
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 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.
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
mplemented in a language other than Java.29. What is final?
A final class can't be extended ie., final class may not be subclassed. A final method can't be
overridden when its class is inherited. You can't change value of a final variable is a constant
30. What if the main method is declared as private?
The program compiles properly but at runtime it will give "Main method not public." message.
31. What if the static modifier is removed from the signature of the main method?
Program compiles. But at runtime throws an error "NoSuchMethodError".
32. What if I write static public void instead of public static void?
Program compiles and runs properly.
Program compiles but throws a runtime error "NoSuchMethodError".
34.What is the first argument of the String array in main method?
The String array is empty. It does not have any element.This is unlike C/C++ where the first element by default is the program name.