|
Java Interview Questions and Answers
What is the difference between final,
finally and finalize?
final is used for making a class no-subclassable, and making a member
variable as a constant which cannot be modified. finally is usually used
to release all the resources utilized inside the try block. All the
resources present in the finalize method will be garbage collected
whenever GC is called. Though finally and finalize seem to be for a
similar task there is an interesting tweak here, usually I prefer
finally than finalize unless it is unavoidable. This is because the code
in finally block is guaranteed of execution irrespective of occurrence of
exception, while execution of finalize is not guarenteed.finalize method
is called by the garbage collector on an object when the garbage
collector determines that there are no more references to the object.
Presumably the garbage collector will, like its civil servant namesake,
visit the heap on a regular basis to clean up resources that are no
longer in use. Garbage collection exists to prevent programmers from
calling delete. This is a wonderful feature. For example, if you can't
call delete, then you can't accidentally call delete twice on the same
object. However, removing delete from the language is not the same thing
as automatically cleaning up. To add to it, Garbage collection might not
ever run. If garbage collection runs at all, and an object is no longer
referenced, then that object's finalize will run. Also, across multiple
objects, finalize order is not predictable. The correct approach to
resource cleanup in Java language programs does not rely on finalize.
Instead, you simply write explicit close methods for objects that wrap
native resources. If you take this approach, you must document that the
close method exists and when it should be called. Callers of the object
must then remember to call close when they are finished with a resource.
What's the difference between the methods sleep() and wait()
The code sleep(1000); puts thread aside for exactly one second. The code
wait(1000), causes a wait of up to one second. A thread could stop
waiting earlier if it receives the notify() or notifyAll() call. The
method wait() is defined in the class Object and the method sleep() is
defined in the class Thread.
The following statement prints true or false, why?
byte[] a = { 1, 2, 3 };,
byte[] b = (byte[]) a.clone();
System.out.println(a == b);
The false will be printed out. Because the two arrays have distinctive
memory addresses. Starting in Java 1.2, we can use
java.util.Arrays.equals(a, b) to compare whether two arrays have the
same contents.
Why do we need to use getSystemResource() and getSystemResources()
method to load resources?
Because we want to look for resources strictly from the system classpath,
These methods use the system ClassLoader to locate resources, which
gives you stricter control of the resources used by the application.
ArithmeticException?
The ArithmeticException is thrown when integer is divided by zero or
taking the remainder of a number by zero. It is never thrown in
floating-point operations.
What is a transient variable?
A transient variable is a variable that may not be serialized.
Which containers use a border Layout as their default layout?
The window, Frame and Dialog classes use a border layout as their
default layout.
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.
What is the output from System.out.println("Hello"+null);?
Hellonull
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.
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.
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.
Is null a keyword?
The null value is not a keyword.
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.
Page Numbers :
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
Have a Question ?
post your questions here. It
will be answered as soon as possible.
Check
Structs Interview
Questions for more Structs Interview Questions with answers
|
