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Abstract class is a partially implemented class so, How can we call an abstract method without creating a subclass.
navneetgoyal2000
- Jan 6th, 2011
I am not sure, but if ABS class can have a static member function (I am not sure either about if ABS class can have static member function), then without instantiating an OBJ of ABS class, the class function can be invoked.Guys, please check it, and update here...It will be helpful for others too.
sayoke
- Dec 12th, 2006
Another useful method is to use reflextion api. But this is not recommended. It will also ask users knoledge to a very lower level.
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Overloading Performance
If Overloading is not going to help to increase performance then why we need to use same name for different methods?
mohit235
- Dec 28th, 2010
Their is no such use for programmer, their is signifigance for user, he/ she has no need to know and remember a lot of method name, one can do different work.
ajay8706
- Nov 27th, 2010
By using Overloading, we implement Polymorphism in Java that is why same mehods can act as differently in situations by using overloading.
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Why was Java Created?
PlatForm Indepentdent ,security,Garbage Collection.
nishant.mca2010
- Dec 17th, 2010
Java was created to make programming simple and easy. Designing the Java simple was the main aim of the Java creator (Java Soft people). When Java was developed, they wanted it to be simple because i...
jimmy514in
- Apr 22nd, 2010
Java is created for simple OOP.It doesnt use multiple inheritance for simplicity hence it is not pure OOP.Java uses JVM, hence it is platform independent.Java uses collections hence it is easy to code...
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Garbage Collector
How does garbage collector decide which objects are to be removed? Can garbage collector be forced?
nishant.mca2010
- Dec 17th, 2010
Garbage collector is used to collect those objects in the Heap memory which is not referenced by any reference variable by calling System.gc() method. The purpose of GC is to delete objects that can't be reached. Only the JVM decides when to run the GC, you can only suggest it.
KhyatiK
- Nov 12th, 2010
Garbage collector removes those objects from heap memory which are no longer referred by any other objects.Using System.gc() you can call garbage collector but its not neccesary that it will run.JVM decides when the Garbage Collector will run.
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Explain working of Java Virtual Machine (JVM)
nishant.mca2010
- Dec 17th, 2010
Java Virtual Machine is the heart of entire java program execution process. It is?responsible?for taking the .class file and converting each byte code instruction into the machine language instruct...
ramakrishnankt
- Apr 20th, 2009
* Creation of bytecode* Verifying the byte code* Linking the code with?library* Maintaining garbage collection
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Find the Output
class A{ public static void main(String[] a){ System.out.print(String.valueOf(1)+String.valueOf(2)); String s1="s1"; String s2=s1.toString(); System.out.print(","+(s1==s2)); }}
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More than One Class
If more than one class is present in one Java file then what will be the java file name?
zshekhtm
- Dec 10th, 2010
You can have more than one class in the same Java source file but only one class can be public in any source file and its name should correspond to the name of a source file. This public class should have main() implemented.
annmary
- Dec 8th, 2010
If a file contain more than one class, the name that file will be the name same as the class which is declared as public. It is not mandatory.
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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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Compare String object with StringBuffer object.
divya_mini4u
- Sep 22nd, 2010
String objects are immutable in the sense once created cannot be changed, whereas StringBuffer object is mutable and can be changed i.e it saves memory space
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Is SQLException run time or compile time exception?
timmireddy
- Jul 14th, 2008
SQLexception that is thrown when SQL Server returns a warning or error. This class cannot be inherited. SQLException comes under Runtime exception because errors comes under Unchecked Exceptions.
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Directories usage information.
Explain the purpose of 'JDK','JRE',LIB' directories.
SoonamK
- Nov 8th, 2010
JDK:Java Development Kit is needed for developing java applications.It includes JRE, set of API classes, Java compiler, Webstart and additional files needed to write Java applets and applications.JRE:...
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HiRecently at an interview I was asked the following question:Create a hashtable A, assign key value pairs to it and then set A to null. Will it be garbage collected?Please reply.
jimmy514in
- Oct 31st, 2010
Objects which have null references are garbage collected ..But you can just request the garbage collector algo to start..you cannot command it..so when it would be collected is not known..Also, a null reference attached to object is called as weak referenceAnd weak references are garbage collected.
vinaymudgil007
- Jun 11th, 2008
Yes the hashtable would be avaliable for garbage collection BUT when actually is would be collected that would depend on JVM garbage collection cycle.vinny
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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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Which one is better when compare with Interface and Abstract class ?
muralidhar.9e
- Oct 30th, 2010
I prefer to Interface. Because the same feature can have different implementations in different Objects.And can also support for multiple Inheritance through Interfaces.If you go for Abstarct Classes ...
salman138
- Oct 29th, 2010
Both Interface and Abstract class have different usages. Interface is used to define that an object support a certain kind of functionality like any class that implements Comparable interface has the ...
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Class hierarchy of HashMap is as follows
"HashMap extends AbstractMap implements Map"
When AbstractMap implements Map interface and AbstractMap is extended by HashMap, what is the use of again implementing Map interface in the declaration of HashMap?.">Class hierarchy of AbstractMap is as follows "AbstractMap implements Map"Class hierarchy of HashMap is as follows "HashMap extends AbstractMap implements Map"When AbstractMap implements Map interface and AbstractMap is extended by HashMap, what is the use of again implementing Map interface in the declaration of HashMap?.
jimmy514in
- Oct 30th, 2010
When you create a concrete class, all the features of abstract classes & interfaces extended earlier have to be implemented, if not already done so..so that purpose of implementing an hashmap again doesnt really suffice the need..please let me know too..
neelam
- Jul 4th, 2006
This is because AbstractMap is the abstract class and not all methods from Map interface are implemented in AbstractMap. Hence HashMap implements Map interface to implement?of the metods in Map interface.
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Scope Variables
jimmy514in
- Oct 30th, 2010
owever the declaration of a member needs to appear before it is used when the use is in a member initialization expression...this is not correct..!!
satyarajasekhar
- Jun 11th, 2006
A variable's scope is the region of a program within which the variable can be referred to by its simple name. The location of the variable declaration within your program establishes its scope and pl...
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Downcasting - Superclass Reference
Explain what is superclass reference to subclass object? Why do we go for downcasting?
muralidhar.9e
- Oct 29th, 2010
Downcasting means using the super class object into the subclass.And we are cating to our sub class object.Like let's assume super and sub classesclass BaseClass{ ---...
manoj.muthavarapu
- Oct 27th, 2010
We extend a class to provide a more specialized behavior for it in the subclass. For example, consider the class "Vehicle" and imagine a subclass "Bus". All vehicle objects are cap...
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What significance of protected Constructors?
jimmy514in
- Oct 27th, 2010
And , I thought constructors were NOT inherited..what probably protected means , is that private..you cannot directly call that constructor..I am unsure, if you can use protected and inherit..please clarify1
jimmy514in
- Oct 27th, 2010
What if I have a scenario?public class A{protected A(String str){//code block}public A(){this("name1");}public static void main(){new A();//now you can use the protected constructor..//or you can also use the static block to call the protected constructor..cant u?}}
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Create Object Using Clone
Give an example of using clone to create an object.
muralidhar.9e
- Oct 11th, 2010
We can create an object by using clone() method which is a object class method.Create an object like MyClass obj=new MyClass();CloneClass cloneobj=(CloneClass)obj.clone();By this way you can create a ...
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What is the difference between abstraction, encapsulation and data hiding?
VishnuPrasad88
- Oct 4th, 2010
1. Encapsulation means Binding the Data with its relative functions. That means only those functions can access the data, and no other function can access that data. This can be achieved by classifyin...
lhariPrasad
- Mar 18th, 2008
Venkat,The thing which you mentioned can also be done by Inheritance, then what is the need of Abstraction over here in Java. Is it that much important ?I feel Abstraction is something where a specific template like structure is created for the implementators, aiming to provide a common interface.
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