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Multiple Inheritance
Why multiple inheritance is not applied in Java?
vinodkashyap
- Jul 9th, 2009
Lets take an exampleClass A{ public void clear(){ }}Class A{ public void clear(){ }}Class B extends A{ public void clear(){ }}Class C extends A{ public void clear(){ }}Now If multiple inhertence is al...
rhingarajiya
- Jul 8th, 2009
In Multiple Inheritance, Diamond problem may arise. So Java supports multiple interface inheritance instaed of multiple inheritance.
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Argument Constructor
What is "no argument constructor " in Java?
arun4u33
- Sep 10th, 2009
If you do not provide any constructor in your program? then compiler implicitly provide an empty constructor(zero parameter).If you writes any default constructor or parameter constructor in your? program then compiler does not provide zero parameter constructor.
ashwini_geeks
- Sep 7th, 2009
The zero argument constructor is used to initialize the class. If we dont write a zero argument constructor also compiler creates one for intializing the variables
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JSP jspinit() method
Will you be able to override jspinit() methods? Justify
apgenius
- Jan 10th, 2010
Yes, we can. Infact its actually why it's there. We override the jspinit() when we want to make some initial database connections etc..Same goes for jspdestroy(), but _jspService() can't be overriden.
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Need of Method Overloading
What is the need of method overloading? What would happen if this feature is not present in Java?
msrmsr
- Oct 4th, 2010
In Java one of the main concept is polymorphismpoly means many..taking many form with existing one.if we use a method callled add();add(int x,int y) we can? add 2 integersadd(float x,float y)we can a...
yogesh249
- Jan 30th, 2010
It is simple. Overloading is required, if you want a particular method to change its behavior based on the parameters passed.Suppose you have a sum functionSum(int i, int j)This will add two inte...
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Object Class
When you declare a class, why does it automatically extends to object class? Give 2 reasons.
mani.sivapuram
- Mar 11th, 2011
When preparing the Java by JavaPeople they thought like every object what we prepare should have some common property so that we can do some basic operations like for example clone() method. So ...
anandkumarjha
- Aug 9th, 2010
Object class is the super class of all the classes provided by java.lang package.? And I think you know that all the basic functions to write a program like println() are the content of the class...
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Runnable Method
If Thread class contains run() method then why we are using run() method by implementing the runnable method in the Thread?
muralidhar.9e
- Sep 29th, 2010
Actually Runnable interface has the method run(). Every thread Object call the start() method to run the thread run() method. So Every run() method have their own implimentation.So we should write their own run() method thread code.
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Size of an Object
How to find size of an object?
rohodium
- Sep 7th, 2010
As there is no predefined method in Java. We can use an indirect approach. We can calculate the memory of an object by taking the difference of the amount of memory used by the program before creatin...
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How to find out classes present in predefined packages?
Kumar
- Jul 24th, 2011
By referring the RT.jar file in jre folder of jdk software installation
vasavimonika
- Mar 5th, 2011
By going through the API we can find out all the prefined classes as well as interfaces and what are all the methods can support by that class.
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System is a class or a package?
class Test
{
public static void main(String... a)
{
System.out.println("hello world");
}
}
In the above code if we write "s" of String class in lowercase, it gives an error of class not found, but if we write "S" of "System" class in lower case it gives an error package not found.
why?amrutabhavana
- Sep 4th, 2011
System is class.it belongs to the lang package."System.out.println" means println is a method which is called by out object of system class.
Prabha
- Aug 10th, 2011
System is a class which is available in lang package and we need not to create object. When we give System as system compiler searches in the package and gives an error.
String is also a class and we can create objects to handle character strings and it is a reference datatype -
What is the purpose of hash code in Java?
rajesh
- Feb 28th, 2012
At the time of creating object constructor will be execute it will tell the size of memory to the JVM and JVM will tell to the heap manager and heap manager will create the memory at that time heap manager will create one unique id is called hash code
amrutabhavana
- Sep 4th, 2011
Hash code is nothing but byte code. The byte code produced in Java is independent of architecture. We can run this byte code in any platform. By this we can say that Java is platform independent.
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Java code to set column width in CSV file
Can someone help on how to set the column width in CSV file using javacode.
I have used FileWriter class to upload data into the csv file. Results are getting populated properly but csv file showing results with default column width. Is there a way we can set the width of the column dynamically based on result length or set fixed length?
Dusmanta
- Nov 12th, 2014
Use Apachae POI jar for this HSSFSheet sheet = workBook.createSheet("testXls");
Code- // Code to Auto size the column widths
Abhishek Mishra
- Oct 8th, 2014
Account,LastName,FirstName,Balance,CreditLimit,AccountCreated,Rating 101,Reeves,Keanu,9315.45,10000.00,1/17/1998,A 312,Butler,Gerard,90.00,1000.00,8/6/2003,B 868,Hewitt,Jennifer Love,0,17000.00,5/25/1...
Explain Object Construction in simple terms
In Java, object types (i.e., classes) must be explicitly constructed for initialization. Explain object construction. Then, state the name of the mechanism for object destruction, and explain in simple terms how it works.
Explain White box testing related to Java ?
Abhishek Mishra
- Oct 5th, 2014
White Box Testing is a software testing method in which the internal structure/design/implementation of the item being tested is known to the tester. The tester chooses inputs to exercise paths throug...
ABHISHEK MISHRA
- Oct 5th, 2014
White box testing is the detailed investigation of internal logic and structure of the code. White box testing is also called glass testing or open box testing. In order to perform white box testing o...
What is lock in thread
Vishal
- Jan 2nd, 2018
When we are working with multiple threads, we have to make sure multiple threads are working on synchronized object otherwise different threads might see different values for same variables. In order...
sandychops
- Feb 24th, 2015
Lock is a thread synchronization mechanism similar to synchronized blocks. From Java 5 the package java.util.concurrent.locks contains several lock implementations which we can use to achieve synchron...
Why do threads block on I/O
Threads block on i/o (that is enters the waiting state) so that other threads may executewhile the i/o Operation is performed.
Read Best Answeramreenkhader
- Jan 20th, 2012
Thread gets blocked just because when two thread try to access the single resource simultaneously the threads get blocked and when one thread is using the resource other should be put to sleep state b...
saravanakumar
- Aug 28th, 2005
Sir, i want one doubt, how to open the new window from click the java frame using handling event. please give the idea to me. i know that it's a comment page. But u have using the doubt page. thanking u.
What is an Iterator interface
The Iterator interface is used to step through the elements of a Collection.
What is the difference between yielding and sleeping
When a task invokes its yield() method, it returns to the ready state. When a task invokesits sleep() method, it returns to the waiting state.
What is a native method
A native method is a method that is implemented in a language other than Java.
What is the difference between the Boolean & operator and the && operator
If an expression involving the Boolean & operator is evaluated, both operands areevaluated. Then the & operator is applied to the operand. When an expression involvingthe && operator is evaluated, the first operand is evaluated. If the first operand returns avalue of true then the second operand is evaluated. The && operator is then applied tothe first and second operands. If the first operand evaluates...
Tracy Nelson
- Sep 7th, 2005
There is no such thing as a "Boolean &" operator. The & operator is the bitwise-AND operator, and combines two values. It's often used for masking off part of a variable (e.g., to get the two low-order bytes of a 32-bit value, use the expression "value & 0xFFFF").
What is the purpose of the Runtime class
The purpose of the Runtime class is to provide access to the Java runtime system.
jimmy514in
- Jul 5th, 2010
I think we can use the runtime to get the properties of the class and also to load a specific .exe file from a particular location.Please let me know if I am mistaken. Thank you.
Suresh
- Mar 30th, 2006
Which returns the runtime information like memory availablilityRuntime.freeMemory() --> Returns JVM Free MemoryRuntime.maxMemory() --> Returns the maximum amount of memory that the JVM will attempt to use.also helps to run the garbage collectorRuntime.gc()
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