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Transient and Volatile.
What is the difference between Transient and Volatile. Does volatile variable is serialized and synchronised.
Sarje
- Aug 14th, 2009
Transient State of an object can be saved (write to any file) if the class implements java.io.Serializable interface. In this case all of the field's value will be saved. If we want any of the fie...
atmarammuduli
- Jun 17th, 2008
Volatile:Threads dont cache method copy of Volatile instance variables. Each time when the var is used the thread gets latest copy.Transient:instance var not serialized ever. After deserialization its value is null(object) or zero(primitive type).
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Usage of Abstract class and Interfaces
In Real time when we go for Abstract classes and when we go for Interfaces
Sarje
- Aug 13th, 2009
If you want to create only abstract methods in a class then use interface and if you want to create some of the methods as abstract and some as concrete then use abstract class.
dyy123
- Nov 14th, 2008
When you don't want to expose the implementation of the methods then you can use the Interface. Abstract class is will have some methods implemented and some unimplemented.
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Static data member
What is the use of static data member?
Sarje
- Aug 13th, 2009
Static data members field (variable) and method belong to class. Static fields can be used before creating an instance of the class and static method can be accessed using class name.
aditya_8584
- Mar 24th, 2009
Static data member has a class scope. A single copy of static data member get shared?within the objects of that class. A non-static member cannot access a static member of that class.
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(1)Can we have more than one connection object with database at same time?(2)Why Interfaces in JDBC have objects?
rammaheswara
- Aug 10th, 2009
Yes, we can have morethan one connection object same time. This is how we implement connection pooling. Poole minimum and maximum numebr of connections.
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Why cant we compare two objects with ==,why we should use only .equals() for objects.
we can compare two Strings with (==) when we assign some string value to the String variable,but if we create an object to that strings and compare eachother we cant use(==) operator ,because we can compare only values with(==) operator but as Objects contains references to that variables we cant use(==) operator,hence .equals() is used on references and (==) is useed on values
geeksterrahul
- Jul 25th, 2009
== operator checks to see if two references are referring to the same location on memory.This is also called shallow comparison..equals checks to see if the two objects match each other. This is also known as deep comparison.
chandanareddy
- Jan 31st, 2006
Both == and equals() can be used to compare objects but in different aspects== is used to check whether the references are aliases.equals() is used to check for object value equality. equals() method...
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It is a saying that static methods in JAVA programs should be minimised. What is the reason for this? any problems arise or there is any performance measures to be looked into it.
geeksterrahul
- Jul 25th, 2009
One simple answer:Static(per class) members are created one instance/class loader/class instance. so they will reside until the class unloads(application closes).Meaning,they will stay during the life...
sunil kulyana
- Jul 21st, 2006
Static variables and classesIn Java, usually a class member (variable or method) is accessed in conjunction with an object of its class. In the case of static variables and methods, it is possible to ...
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Why ArrayList is faster than Vector?
meSubhadip
- Jul 21st, 2009
Vector is synchronized so JVM needs to take extra care to acquire and release locks to make vector thread safe. But ArrayList is not synchronized so JVM doesn't need this extra overhead.That's why arraylist is faster than vector.
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What are the differences between C++ and Java
meSubhadip
- Jul 20th, 2009
The main differences are:?Java does not support typedefs, defines, or a preprocessorJava supports classes, but does not support structures or unionsJava does not support multiple inheritanceJava does...
lalitsonawane27
- Feb 7th, 2009
C++ is not a platform independent language while Java is platform independent language.
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Array List Collections
What is Use of declaring an array list object like List list = new ArrayList() rather than creating object like ArrayList arr = new ArrayList();
shailesh.pandit
- Jul 11th, 2009
We may decide later to use the?LinkedList instead of ArrayList, in this situation we just need to replace the new ArrayList() part with new LinkedList() if we keep the referance variable as List interface.whereas if we keep ArrayList as the referance variable it will be cumbersome.
R.Raj
- Jul 5th, 2008
Yes,It is possible to invoke the methods of ArrayList using the reference variable list.Infact it is used for that purpose only.
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Explain interthread communication.
Radhakrishna P
- May 11th, 2009
When threads are running in shared resources we can manage the threads by using native methods (wait(), notify(), notifyAll()) from Object class.This is inter process communication between the threads while sharing shared resources
AjayMukiri
- Apr 30th, 2008
Java provides a basic set of synchronisation methods within java.lang.Object, allowing threads to wait for notification from other threads. Using the wait() and notify() methods, threads can synchroni...
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How can we call multiple applications using simple command in java
VenkitaKrishnan
- Apr 20th, 2009
Create a batch file and write down all the applications which needs to be called. Simple isn't it?
ramesh.sukka
- Apr 16th, 2009
Write Java Threading Application in which you can invoke multiple Java Application at time. so from Command promt if you execute Thead application, internally it will executed multiple application.Regards,Ramesh Sukka.
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Every application should have a main() method. Under which class does the main() method comes under?
shouvanik1979
- Mar 31st, 2009
Main() method should be present in the java class which we execute at the command prompt. for example. c:/> java abc where abc is the class which must have a main() method, because JVM calls the main method of this class after it loads all the classes into its memory.
vawani
- Nov 4th, 2008
If you are writing a program in java then you have to put main method in a class, so that class is the owner of main method but since we r declaring it as public it is available to a...
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What is Shallow cloning in Java ?
TypeEE
- Feb 11th, 2009
By default, cloning yields a shallow copy. By shallow, we mean the object is copied, but the contained objects are not. What a deep copy does it copy the cloned object, as well as all the objects with...
Naveenjavasun
- Jul 8th, 2008
When we need a copy of the object we go for cloning. When an object is shallow coned the parent object or top level object and its members are duplicated, where as the low level objects are not duplic...
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What is the basic difference between Java and .Net
akhilmisra
- Feb 8th, 2009
JAVA is platform independent while .Net works only for the MS platforms. .Net supports an array of languages while for working with J2EE you have only one option and that is 'JAVA". .Net work...
krupananda
- Jun 17th, 2008
No thats not true. Java has a byte code editor too.. Refer : http://www.cs.ioc.ee/~ando/jbe/
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How all can you free memory
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What's the difference between Object and "E"?
I'm trying to write an Iterator class for a LinkedList class that I wrote.One of the methods is "public E next()"I try to return an "E" but eclipse says "cannot convert from Object to E".How do I fix this?
kabir soni
- Feb 6th, 2009
Object is a class and E is a generic type parameter . And Iterator class alwayes return Object so to fix this problem, you need to call it. For exampleimport java.util.ArrayList;import java.util.Itera...
shishir11485
- Aug 5th, 2008
Object having a reference of one variable store in stack whereas "E" is created in a heap don't have a reference variable
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What is Externalization?
jay
- Sep 23rd, 2006
Externalization is a more advanced alternative to serialization.Basically, externalization gives you more control over serializating stream than default serialization (as by implementing Serializable ...
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Difference Between Collection and Legacy classes
What are the difference between Legacy classes and Collection other than Synchronized?
udaya.kumar
- Dec 12th, 2008
Legacy Classes : Previously Collection Frame Work was not part of java.util package. Later some of the classes were re-engineered Known as Legacy Classes. Legacy Classes are SYNCRONIZED(Ctrlng accessibility over the resource).Ex:Vector/Stack/Hashtable/Dictionary/Properties.
sampra
- Feb 11th, 2008
legacy class are syncronized by defult where as collection's member are not syncronized by deflt
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What is markup interface? What is the purpose of markup interface?
sunil_jsr123
- Aug 25th, 2008
In Java language programming, interfaces with no methods are known as marker interfaces. Marker interfaces are Serializable, Clonable, SingleThreadModel, Event listener. Marker Interfaces are implemented by the classes or their super classes in order to add some functionality.
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Supplying Arguments to Main Method
What is the meaning of supplying string[] args to main method?
dugulam
- Dec 6th, 2008
public static void main(String args[]) This array of Strings is the mechanism through which the runtime system passes information to your application. Each String in the array is called a command ...
Core Java Interview Questions
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