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What is the difference between Inheritance and Aggrigation?
vinaymudgil007
- Mar 21st, 2011
Inheritence means --> "is-a" relationshipe.g. HONDA CITY is-a CARAggregation means --> "has-a" relationshipHONDA CITY has-a engineHope this makes it clear !!!
navneetgoyal2000
- Jan 5th, 2011
If we have to explain it with example, then Inheritance (IS A or TYPE OF) & Aggregation (HAS A) can be understood as:a CAR IS A (an) Automobile. (Inheritance: Car inherits its properties from Automobile)Whilea CAR HAS A (an) engine. (Aggregation: Car Class has an Object of engine class)
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What are some alternatives to inheritance?
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What is serilization and deserilization
sampra
- Feb 22nd, 2008
Taking object state in flat file is serilization where as reconstructing new obj wt that data is deserlization
sujatham
- Aug 2nd, 2007
To serialize an object means to convert its state to a byte stream so way that the byte stream can be reverted back into a copy of the object. A Java object is serializable if its class or any of its ...
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//this.disp();
}
void t3()
{
System.out.println("Enter to t3 void");
}
}
On what situation void type constructors are used?">Class t3{ int i; static public void main( String a[]) { int j=8; t3 t= new t3(); new t3().disp(j); } //constructor overloading t3() { System.out.println("Enter to t3"); //this.disp(); } void t3() { System.out.println("Enter to t3 void"); }}On what situation void type constructors are used?
vinaymudgil007
- Jun 12th, 2008
Constructor's don't have any return-type....... and hence when you precede void with constructor java comipler treats it as a METHOD of that class and not as constructor!!!vinny
chinnu
- Nov 18th, 2006
Actually constructor means one type of special methods in java. It returns nothing even void also. These are used for intilising the objects with same parameters and different parameters.
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Why class Class is always the Super Class for every class
ashish
- May 20th, 2012
1. Object is super class for all java classes.
2. even if someone want to make a class as subclass of CLASS class, he cant because class class is declared as final. so it can not be inheritedvinaymudgil007
- Jun 12th, 2008
Java.lang.Object is the super class of all classes and NOT Class classvinny
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Which marker interface in java is having methods in it
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Market interface means interface which have no methods. Then why we call the Runnable interface as a marker interface, even though it has run() method
pdommara
- May 31st, 2010
Who said Runnable interface is marker interface. It has method called run(). It is not a marker interface.
piscesinblues
- Jan 22nd, 2007
Up to my knowledge marker interface is an interface having no methods, so Runnable interface is an interface having run() method, so definetly it is not a marker interface, if so the case, please post the complete description regarding that and let me know
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What is the difference between dynamic method dispatch and method over riding?
vinaymudgil007
- Jun 9th, 2008
Sampra -- what you said is correct but don't you think that over-ridding itself uses dynamic method dispatch....what i am trying to say is that the line demarcation is very thin.vinny
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What are advantages and usage of static block?
pdommara
- May 28th, 2010
The above answers are missing important point that is it even runs before your class constructor.
vinaymudgil007
- Jun 10th, 2008
static block is executed whenever a class is loaded by the JVM.....hence in case you want certain code to executed or say some objects of a class avaliable to ur application as soon as the application starts you can put in the relevant code there....vinny
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What is the use of writing empty catch block?
vinaymudgil007
- Jul 31st, 2008
Just catch the exception & swallow it [don't take any action].that's all.vinay
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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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Differences between HashList and HashMap, Set and List
nnandurkar
- Jun 23rd, 2010
Hashtable is syncronised where as HashMap is not. Hence, HashMap is faster.Hasttable does not allow any null value as either key or value. However, HashMap allows multiple null values and one nul...
kayalsuku
- Jun 2nd, 2008
HashMap is an unordered and unsorted map. Allow one null key and many null values. Lists are collections that maintain their elements in order, and can contain duplicates. Set interface do not a...
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What is data encapsulation? What does it buy you
ragini.rani
- Mar 13th, 2006
encapsulation mean data hiding.data correspond to varibles and methods of the class. Data hiding mean: when u make different objects of the same class. The data stored in one object is unaware of the data for other object of the same class. In, this way it gives secure data.
Devidas Sonawane
- Oct 28th, 2005
Encapsulation:- it is a mechanism to binds data and bytecodes and b'coz of that data is protected and becomes secure.
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Would you like to derive data from a base class
biman786
- Aug 14th, 2010
If the Base class and super class are within same package, then data of super class should be public or default or protected. But if base and super classes are in different packages, then?then data of super class should be public or protected.
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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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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 is the difference between Enumeration and Iterator?. When i can use Enumeration and when i can use iterator?. Can any one tell me the situation that only Enumeration could able to solve that problem and vice versa.
In Enumeration we cant modify the elements. where as in iterator we can modify the elements
guls.naikwadi
- Dec 27th, 2009
Both are used to traverse objects one by one but Enumeration is a legacy classes and it comes with Java1.1 Iterater they have introduced in Collection framework. Enumeration can be used for Coll...
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How can u tell HashTable is Synchronized?(IBM-chennai)
John
- Apr 3rd, 2007
HashTable is synchronized
Core Java Interview Questions
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