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In How Many ways can we create an OBJECT in Java ? Illustrate.
sampra
- Feb 14th, 2008
perfect ans:Here is the list I formed: 1) using new 2) Serilaization 3) Shallow cloning 4) Deep cloning ý same is serialization 5) Reflection/ Class.newInstance()
Sagar
- Nov 27th, 2007
Here is the list I formed: 1) using new 2) Serilaization 3) Shallow cloning 4) Deep cloning ? same is serialization 5) Reflection/ Class.newInstance()
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What is the need for calling default constructor by JVM? why the JVM should intiializes default values to the data fields if the constructor is not there in our class?
sampra
- Feb 14th, 2008
use of default constructor is to create the default object of type java.lang.Class which is done by JVM
Raghava
- Nov 20th, 2007
First, Let us understand the concept of construcotrs. The constructors are used to construct objects. This is the Only way to create object. If we did not write any constructor in our class, the compl...
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Can we declare an interface in servlet
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Why should we extend Exception instead of Throwable?
We usually extend Exception instead of Throwable. Why? In what situations we extend Throwable.Could anybody give the answer in detail. Thanks in advance.
shweta.suryanarayanan
- Oct 1st, 2008
By extending Throwable, you are giving hook for RuntimeException and programmers normally do not catch unchecked exceptions. However, if you have an app server and want to en...
rariedel
- May 27th, 2008
Extending the Exception class (a descendant of Throwable) instead of extending Throwable itself is a programming convention, not a requirement.Like most conventions, following the convention lends consistency to the end result.
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Difference between throw and throws
What exactly is the difference between between throw and throws? If both are used for the same purpose then why are both needed instead of one?
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Editorial / Best Answer
vegetto- Member Since Jun-2008 | Jun 15th, 2008
hi there,
throw:the throw keyword is used to throw the exception manually,that is when you feel a particular line in your code, when executed is capable of having some exception then you use throw keyword as:
throw new MyException(arguments if any);
this leads to instantiating of the MyException class and exception is thrown
throws: this is to be used when you are not using the try catch statement in your code but you know that this particular class is capable of throwing so and so exception(only checked exceptions).in this you do not use try catch block but write using the throw clause at appropriate point in you code and the exception is thrown to caller of the method and is handeled by it. eg:
void trouble()throws IOException,any other exceptions just separate them with commas.......
{
/* throw statement at appropriate step,
no need to use try catch here,exception would be thrown to caller and u should provide try catch block to handle exception there else this process cotinues further till
appropriately it is handeled or prog terminates abruptly */
}
this is called as HANDLE OR DECLARE RULE i.e either u handle exceptions using try catch block or by declaring them
vegetto
- Jun 15th, 2008
hi there, throw:the throw keyword is used to throw the exception manually,that is when you feel a particular line in your ...
krishna_kanth83
- Jun 14th, 2008
they are not same."throws" declares that your method is capable of throwing an exception."throw" actually does the work , of throwing the exception.example :public void...
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Read Number Methods
How many methods to read numbers and characters and what should be used.
Sarje
- Aug 17th, 2009
Methods in InputStream to read byte and in Reader to read character are -int read()int read(byte buffer[])int readIbyte burrer[],int offset,int numBytes)
inthiyaj
- May 9th, 2009
We have readers and streams. Readers are used to read characters and streams are used to read bytes, streams returns numbers i.e. byte number.
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Command prompt argument
How to pass commandline arguments in main function through Eclipse Tools (editors).
nookashiva
- Sep 14th, 2008
Click the Run menu barNow click the Open Run DialogueA new window will be opened.In that window click the Java applications thenA new sub menu will be opened in that select Arguments menu andType the Arguments with space.Click run to view your result in the console.
Gokul44
- Jul 18th, 2008
Click the run menu barnow click the openrundialoguea new window will be opened.in that window click the arguments menu and type the arguments with space.click run to view ur result in the console.
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What is the purpose of singleton design pattern?
mani.sivapuram
- Feb 10th, 2011
Singleton design pattern is used to create only one instance.I want to a an example when we are using this singleton design pattern in real life.generally the dao classes like insertDao,updateDao,dele...
shreesha.s
- Sep 5th, 2010
Singleton Design Pattern is used when we would like to have a single instance. A class distributes the only instance of itself. It will be used with Connection Pool usually.
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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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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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Importance of java.lang.obj
What is the significance of java.lang.object class?
sampra
- Mar 6th, 2012
Java.lang.Object provides several methods which are common to objects. java.lang.Class object is created whenever JVM creates an object.
Lokesh M
- Nov 29th, 2011
java.lang.Object provides several methods which are common to objects. java.lang.Class object is created whenever JVM creates an object. java.lang.Class is a superclass of all objects and it describe...
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What are the roles and reasons for using Annotation in Java? Give real time demonstration example
sampra
- Mar 13th, 2012
In the annotaion we are providing the meta data. this job previously done in xml file which causes lot of mentenece.so benifit of annotaion is to mainly provide the meta data information in java file and reduce the mantinence
- Oct 28th, 2011
The usefulness of annotation can be found in J2ee,where we deal with xml files. To get the value from xml files,j2ee technology uses parsers like xerces,jdom,sax etc.Working with parser is always a h...
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Implement and Extend Keywords
What is the implement, what is the extend keyword, what is the difference, give me answers in briefly ?
sampra
- Mar 6th, 2012
Implement key word is use when we have to implemet interface in that class. else we are using extends
Shivang Modi
- Oct 5th, 2011
A class can extend an another class but a class can implement an interface.
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Database Driver
How to find which type driver used in Java or J2EE applications? Which type used commonly?
Lokesh M
- Nov 29th, 2011
Java.sql.Driver interface used to find and use the JDBC driver for a database. Oracle thin driver is commonly used
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Abstract class and interfaces
Where should we use exactly abstract class and interfaces?
rpmnitp
- Jul 13th, 2012
Interface is more generic in comparison to the Abstract class, hence when we want our implementing class to implement all the methods we should use Interface.
yuvaraj
- May 11th, 2012
All the methods declared inside an interface are abstract whereas abstract class must have at least one abstract method and others may be concrete or abstract. b) In abstract class, key word abstract...
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MVC architecture
what is the difference between MVC1 & MVC2 in Java?
sivapurammani
- Jul 10th, 2013
MVC(Model-View-Controller) :: This type of architecture makes our code to be reusable and separation of code. View :: Which presents the modal data, example if we are presenting any tabular data or c...
Prasad MN
- Mar 11th, 2013
MVC1: Its a model view Controller architecture 1 that means all the presentation logic and business logic is mixed up. If any modification is required on its impact on the logic. Difficult ...
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How Treeset implementation maintains unique elements in it?
How an Treeset maintains the unique element? Which algorithm does it use?
What is the advantages over doing the same using the Arraylist manually?Prasad MN
- Mar 11th, 2013
Tree Set using internally HashTable for storage the objects using of key and values. Internally its using hashing mechanism. It displays the order on Ascending order.
Nikhil
- Feb 20th, 2013
It uses Red-Black tree alogorithm.
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Sub Class method call
When the Subclass method is called, does the SuperClass constructor execute? If so, which Constructor executes first (Sub Class OR Super Class) for the given below scenarios?
a. Given that we are NOT inheriting SuperClass constructor?
b. Given that we are inheriting SuperClass constructor?Shrimp
- Apr 1st, 2016
When a sub class method is called from parent class, constructor will be executed dude, constructor only executed when you create an object
Manjunath_7_89
- Mar 25th, 2016
Super class constructor could be invoked only when super() is used and it has high priority of invoking, once super class constructor is invoked the setted public/protected variables are inherited in subclass
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What is the use of static block?
sampra
- Feb 15th, 2008
static block is the set of stmnt between {} and declared as static its exceute at class loading time
sujatham
- Aug 10th, 2007
The primary use of static initializers blocks are to do various bits of initialization that may not be appropriate inside a constructor such that taken together the constructor and initializers put the newly created object into a state that is completely consistent for use.
Core Java Interview Questions
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