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What do mean by polymorphism, inheritance, encapsulation?
Polymorhism: is a feature of OOPl that at run time depending upon the type of object the appropriate method is called.Inheritance: is a feature of OOPL that represents the "is a" relationship between different objects(classes). Say in real life a manager is a employee. So in OOPL manger class is inherited from the employee class. Encapsulation: is a feature of OOPL that is used to hide the information.
gvjava
- Dec 8th, 2010
We can't create the object directly for the abstract classes,we can create object indirectly when we are inheriting that is called as polymorphism. ex: abstract class man ...
veenanimbalkar
- Dec 6th, 2010
Polymorphism is the major pillar of OOPs and Java. There are two types of polymorphism static time polymorphism & dynamic type of polymorphism. Static time polymorphism is called as" method overloa...
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Private class SampleA { }class SampleB extends SampleA { }What is wrong in the above code?
Shirshendu
- Sep 14th, 2006
A top level class in Java cannot be a private class
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Public class A {int x; public static void main(String args[]) {x=x+1;s.o.p(x);}}what is the output? a) compile time errorb) runtime error
sekhar511
- Dec 10th, 2010
A non-static variable cannot be referenced as a static contextHence "x" is a non-static variable....
satyanarayana
- Aug 14th, 2007
Compile time errorIn that program int x is an nonstatic variable we can't call directly with static method
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What is the superclass of an exception?
bala
- Apr 29th, 2005
Throwable class
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If 10 threads having equal periority and waiting for one particular object (source ), How the source will notify to the particular thread.
sekhar511
- Dec 10th, 2010
By using synchronization concept we can give object locks to only one thread
gopalakrishnan
- Oct 5th, 2007
If 10 threads are waiting for same priority to access a same resource, at that time the control?have a FIFO order by the threads to access a resource.
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Can consturctors have below modifiersa) finalb) voidc) static
sekhar511
- Dec 10th, 2010
Constructors cannot have return types and modifiers where final, void, static are not allowed as modifiers to constructors.
pramod.cbit
- Mar 22nd, 2008
no..construtors are meant for creating objects and it is not a method but loojk likes method. 1.so u cant put final to other than method,vaRIABLE ,class. 2.if u put satitic means u r breaking ...
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Any 2 errors and exceptions?
varsha
- Jun 13th, 2005
Stackoverfolw,stack underflow r Error.and nullpointerexception,arrayoutofboundexception r Exception.
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Class A{Public void meth(){}}class B extends A{ Public void meth(){ } public static void main(String args[]){ A a=new A(); a.meth();//which method will this call } }if u want to call a method of class B then how can u achieve this?
sekhar511
- Dec 10th, 2010
This problem is known as "ambiguity problem"We can overcome this by using Interfaces.
bhuvanamsk
- Nov 23rd, 2010
To access a method of derived class create object for class B. B b=new B(); b.meth(); If we access class A 's method meth() will not be called.Subclass B overrides super class. to ac...
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Which is the most convient way to create a thread and Why?1) Extends from thread or2) Implements from Runnable Interface.
nkkaushik
- Jan 5th, 2011
Impelementing the Runnable Interface gives a better way to create a Thread because by doing so, you can also extend any other class.
deepthis594
- Dec 27th, 2010
Implementing runnable is the most efficient way to create thread because classes should be extended only when they are being enhanced or modified in some way, while implementing runnable it is only required to override run method.
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Can Abstract class contain a private constructor?
navneetgoyal2000
- Jan 6th, 2011
I suppose yes, an ABS class can have a Private Constructor, AS LONG AS there is another C'Tor in the ABS class, which is PUBLIC AND, derived class C'TOR is written in a way, to call only PUBLIC C'TOR of ABS class.I think, we should check it on programming, for better understanding.
rajesh
- Nov 4th, 2005
Hai,an abstract class cant contain a private constructor bcs, as the abstract class is to be subclassed and when the object of the subclass is created the constructor of the super class is called ...
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What is garbage collection
Ganesh MN
- Jan 6th, 2011
Garbage Collection is the automatic memory management system by which JVM discards unreachable objects(objects which are not being referrenced by any reference varible).
Ritesh
- Jul 25th, 2005
Java provide a automatic clean up of object if that object referecne counter becomes zero. and this is done by the garbage collector. this will invoke automatically and free all those resources(object) who is not been use for a long time..
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Is servlet threadsafe?
sheshccna
- Jan 12th, 2011
Servlets are not thread safe. If you want to make it Servlet as Thread safe, you can implement SingleThreadInterface which is a blank Interface there is no methods (this is not recomend method, bec...
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Servlet Lifecycle
What is the Lifecycle of a Servlet?
invincible_virus
- Jan 22nd, 2011
The life cycle of a servlet is controlled by the container in which the servlet has been deployed. When a request is mapped to a servlet, the container performs the following steps. Loads the se...
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How to convert .class to .java?
How to convert or achieve the program from .class file??
geek_ani
- Feb 1st, 2011
You can?view your .jar or .class files using a Java decompilor. Download the Java decompiler and use it to view these files.
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What is the difference between HashTable and HashMap?
bhushanamca
- Oct 3rd, 2009
Hashtable does not allow null values or null keys, whereas hash map allows null keys and null values. Hashtable is synchronzied whareas hashmap is not synchronized. In case of single thread using hashmap is faster than the hashtable. In case of multiple thereads, using hashtable is advisable.
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Java supports multiple inheritance
Skill/Topic: InheritanceA) TrueB) False
nverma
- Feb 17th, 2011
False, Java doesn't support multiple inheritence..C++ supports multiple inheritence
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What happens when a thread cannot acquire a lock on an object
If a thread attempts to execute a synchronized method or synchronized statement and isunable to acquire an object's lock, it enters the waiting state until the lock becomesavailable.
acevedogalan
- Feb 25th, 2011
It goes to blocked state as it can not continue.but the cpu scheduler will wake him up once in a while .every time he wakes up he will try to get the lock again until he can finally get it.if he never...
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Code for creating a simple Calculator in Java Script.
Ram prabesh sah
- Jun 23rd, 2009
import java.util.*;import java.awt.event.*;import javax.swing.*;public class calculator1 implements ActionListener Runnable{JLabel l1 l2;String s1 "" s2 "" s3 "" s4 "...
BHASKAR CHAUHAN
- May 30th, 2007
import java.awt.*;import java.util.*;import java.awt.event.*;import javax.swing.*;public class calculator1 implements ActionListener,Runnable { JLabel l1,l2; String s1=""...
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What is the difference between OOPS and OOP
ravi mishra
- Mar 7th, 2011
OOps is the methodology to develop systems, the system developed are called object oriented systems. On the other hand oop is an approch for writing the instructions..
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