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Abstract Class or Method
Can we make use of "this" keyword reference inside a abstract method or abstract class? Explain
java indian
- Mar 10th, 2010
Yes we can use "this" key word in Abstract class or methods,Here we have simple sample used of this key in abstract.abstract class ab { int j;void meth() { this. j=10; ...
yogesh249
- Jan 24th, 2010
Yes that is true that we cannot create object of an abstract class. But the question is "Can we use this keyword in an abstract class."The answer is YES we can..Have a look at the following ...
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1) write a program that singleton objects returns two instances?
Give me answer
ksureshbabu
- Mar 5th, 2010
class Singletones implements Serializable{ /** * */ private static final long serialVersionUID = 6240073482570369797L; &...
Jagdeep Grewal
- Nov 8th, 2005
public class CSingleton { private static CSingleton inst= null;private static int count=0;protected CSingleton() { &n...
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Inherit Super Class Without Extends Statement
If Object is the super class of all classes, how it is inherited without extends statement?
santosh.dhulipala
- Mar 5th, 2010
During the compilation process our JVM checks whether we are extending any class, if not it will will extend the object, which we know that is super class of all classes, which is defaultwe can check ...
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What is the use of Empty Interface?
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Run the Tomcat Server
Hi, Is it possible to run the 2 tomcat servers simultaneously with different ports.Some times it's working. some times its not running,Anybody can help me to solve this problem.Thxregards'Punitha.R
DVishwakarma
- Feb 24th, 2010
Multiple instances of tomcat server can be run on any machine using the following steps.Copy zip installer from Apache.orgunzip in C:/Tomcatset Environment variable as CATALINA_HOME C:/TomcatJDK_HOME ...
uncer
- Jan 17th, 2010
Follow these step;1. Set JAVA_HOME=C:/JDK2 SET CATALINA_HOME=C:/TOMCAT3. CLASSPATH=C:/servlet.jav;.;jsp.jar;Then go into tomcat folder search servlet.jar copy short cut paste at desktop and double click.
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Difference: Java Beans, Servlets
lieutaryan
- Feb 13th, 2010
Servlets are java classes designed to serve content from the web, like a web server serves HTML pages. A servlet is used to receive requests, process them, and then return responses to the program tha...
prem kumar
- Jul 29th, 2006
HIWhat is meant by reusable? we can use instance of a class as we want more times. Then, and diff between bean and class.Prempremkumar.cm@gmail.com
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Is it possible to serialize a single member in a class?
suppose i have 2 members in my class can i serialize a single member? Is there any way to do that?
ashutoshwithashi
- Feb 13th, 2010
Yes, it is possible to serialize a single member in a class from the externializable interface as we can control the searization process with the and by searilizing the single memer through writeExternal() and readExternal() method we can do it.
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Will there be a performance penalty if you make a method synchronized? If so, can you make any design changes to improve the performance
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Editorial / Best Answer
Answered by: Faisal Ghauri
- Jul 24th, 2005
Performance does take a hit when using synchronization. I think the way to reduce this hit is to synchronize only a block of code that will be accessed by threads and not synchronize the entire method.
sumeesudha
- Feb 6th, 2010
There is degradation in performance when you make a method synchronized. Even when a program contains only a single thread running on a single processor, a synchronized method call is still slow...
sripatnaiky
- Feb 4th, 2010
The Synchronization may be useful in avoiding the deadlock, helpful in maintaining the consistent object state etc,. Only one thread will be accessed at a time by acquiring lock on the synchronized bl...
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What is the Output of the following Java Program
public interface I1{Static String x="inside I1";public void someMethod();}class A implements I1{ public static void main(String args[[]){ System.out.println("Calling I1 var ..."+I1.x);}}
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abuthahir.d- Member Since Jan-2008 | Apr 14th, 2008
Compilation error due to 2 reasons.
1. All variables defined in the Interfaces are implicitly public static final. So need not specify "Static" in interface.
2. If any of the member functions of a Interface is not Overriden , a compilation error will be thrownshanu_rastogi
- Feb 3rd, 2010
It is right that you dont need to explicitly define a varible static but if you do so then it will not give compliler error..
sarojmohanty
- Nov 19th, 2009
Compilation error will come because you must have to override the abstract method of the implememted interface. After the implementation of the abstract method the program will compile and run properly and print "inside l1".
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What are the differences between weak reference, soft reference and phantom reference
uncer
- Jan 28th, 2010
The garbage collector might or might not reclaim a softly reachable object depending on how recently the object was created or accessed, but is required to clear all soft references before throwing an...
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Marker Interface
When there is no methods in the marker interface, then what is the use of marker interface. What is the functionality of the interface. Why do we need to implement marker interface?
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Saroj_mi2- Member Since Sep-2009 | Sep 14th, 2009
Marker interface is an interface with out having any implementation methods.
By implementing this interfaces, we will specify some special behaviour to implemented class.
Examples: Serializable, Cloneable
For example if we want to create a clone for a an object of class using clone()(clone()-- which is an object class method), then class need to implement Cloneable interface.
This mark is to JVM to handle the interface.If you are implimenting this interface the compliler will know some specific job need to be done.
For Cloneable interface even it does not have any methode the JVM looks for clone() method to execute. But the complier will not fail if the clone() meth is not implimented.
Narotam
- Jan 19th, 2010
Marker interface do not have any method. It is used only to inform JVM that?such class can do some special function like clone, serialize.
uncer
- Jan 15th, 2010
When you need to perform some behavioral function on any class without implementing method in implemented interface we implement an interface such interface called marker interface for exmple serializabe, cloneable.
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Whether private,protected method can be overloaded,overrided or not?Tell me reason?
uncer
- Jan 15th, 2010
A Private Protected Methods can be overloaded but in the concept of overriding access modifier should not be restrictedmean:If a method in superclass is public then overrided method in subclass must b...
Sarje
- Aug 12th, 2009
Private protected methods can be overloaded and overrided. But while overrding method following rules must be satisfied We can not narrow the accessibility but can be widen. Means if the access specif...
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Why java is not 100% oops
smartcasanova
- Jan 13th, 2010
Because of the promitive data types provided in the java such as int, char float, these primitives are not objects hence Java is not pure OO.
sahit
- Oct 27th, 2009
Java does not support multiple inheritance as well as operator overloading, so we can say that Java is not completly supporting OOPs.
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What is the Difference between Design Pattern and Architecture? Can any one answer for this plz..
Design Pattern means how u r approaching the problem.Architecture means how the data is flowing in your application
sambitsahu
- Jan 5th, 2010
Design Pattern:A design pattern suggests a solution for a recurring design problem in an application and the solution is generally open for future extensions.Architecture:It's an outline of an app...
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What is the meaning of "final" keyword?
sambitsahu
- Jan 5th, 2010
Final Variable :: ConstantFinal Method :: Can't OverrideFinal Class :: Can't instatiate
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How hashtable is synchronized?why hashmap is not synchronized?Can we make hashmap synchronized?
karthi1106
- Dec 10th, 2009
Vector/Hashtable Original classes before the introduction of Collections API. Vector & Hashtable are synchronized. Any method that touches their contents is thread-safe. ArrayList/HashMap So...
ssubhajit
- Nov 25th, 2009
Use the Code below to make a Hashmap synchronized ...Hashmap objHashmap = Collections.synchronizedMap(new HashMap(....));
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Why wait and notify method in Object class
Why wait and notify method in Object class, why these are not in Thread Class.
sujithkthomas
- Nov 13th, 2009
Inter thread communication is not directly supported?by the producer or consumer, but by the object they are acting upon. Also lock is associated with a particular object. If a thread needs a lock it use sync block and release using object's methods.
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Wrapping an Object
What does "wrapping" an object mean?
SreerangKulkarni
- Oct 29th, 2009
When an object A is said to "Wrap" object B, it means that Object A HAS A reference to the Object B and deligates calls to it.
karthik_knight2000
- Dec 3rd, 2008
Wrapping an object means we are covering that object, say for example? in Java we can say?String is a class as well as?String is a data type.String s;?? // here s is object of String class ???...
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Meaning - Abstract classes, abstract methods
jawaharl0207
- Oct 25th, 2009
Abstract Class: There are two ways to create abstract class, one is by mentioning abstract key before the class declaration, and second one is by mentioning abstract key before the method declaration ...
haruto
- Oct 22nd, 2009
In java a class has a well defined structure and behaviour. There are times where we do not need to implement a method such methods are written in the class where the class is preceded by keyw...
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I want to know output of this program and the flow alsopublic class Aquestion { private int i = giveMeJ(); private int j = 10; private int giveMeJ() { return j; } public static void main(String args[]) { System.out.println((new Aquestion()).i); } }
talktoatish
- Aug 16th, 2009
public class Foo { private static int j = 10; private static int i = giveMeJ(); private static int giveMeJ() { System.out.println("in the method" + i + j); return j; } public static void...
Core Java Interview Questions
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