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How to compare Stringbuffer objects?
Sarje
- Aug 19th, 2009
Since java.lang.StringBuffer class does not override equals(Object obj) method of the Object class then so you can not compare its objects directly. If you want to compare its objects then first conve...
rameshbabukm
- May 26th, 2007
The Known fact is the stringbuffer strore the data as charcter array, so when when we do a append on the stringbuffer object it inserts the chars into that array.Thats why we got method which can very the initial capacity of the same.hope it clarifies the doubt?
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Does Java have "goto"?
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How i can validate the user, Is there any java api is there for that. Or i can use my one business logic. If both are possible, Then which one is the best way for real time.
Need some information
Sarje
- Aug 19th, 2009
If you are talking about the web application and you are preparing it using JSP and Servlet then you have to write your own bussiness logic to validate the user information. For server side validation...
chowdary
- Nov 8th, 2005
Our own business logic is the best solution because it is more efficient than the api.java Api is common for all,so it may not efficient for all but ur logic is best for ur project.
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What is mutable and immutable in Strings?
Sarje
- Aug 19th, 2009
immutabe string means once string is created you can not insert or append or remove any character from the string. Since java.lang.String class is immutable thess operations are not allowed in it.muta...
sunil belurgikar
- Sep 29th, 2005
Mutable string means we can append to that string.example StringBuffer object is mutable string.String is immutable objectwhen we declre String="abc"; a string object abc with fixed length is created.We cant add anything to it .If we do java simply creates a new object.
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Implement Interface using Polymorphism
How an interface can be implemented using polymorphism?Why multiple inheritence is not used in Java?
Sarje
- Aug 18th, 2009
I think your question is how to achieve Runtime Polymorphism using using interface.then the answer is :interface MyInf{ void show();}class A implements ...
shouvanik1979
- Mar 30th, 2009
Polymorphism means "one form many actions". Lets say, a class Test implements an interface ITest. Accordingly,public interface ITest{ public void testMethod();}//a class implemen...
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What type of access specifiers can we use for local variables?
Sarje
- Aug 18th, 2009
Local variable cannot be modified using any of the acceess specifiers means you can not write private or protected or public before them.Local variables are by default (implicitly)? private no need to make it explicitly private or protected or public otherwise it won't compile.
er.mukesh_208
- Aug 3rd, 2008
Local variables (including formal parameters) are visible only in the method, constructor, or block in which they are declared. Access modifiers (private, public, ...) can not be used with local var...
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Restrict a Class
How can we restrict a class so that no instance creation of class possible without declaring the class as Abstract ?
Sarje
- Aug 18th, 2009
Only abstract classes can not be instantiated. If you make the constructor private then you can not instantiate it outside of the class but you can still instantiate it within the same class.
sriragv
- Jun 21st, 2009
1. By creating a private constructor2. By giving abstract key word to the class
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How to make a class immutable (like String)?
Sarje
- Aug 18th, 2009
immutable means once object is created then you can not make any change to it. if you try to do so then new object will be created and original object will be lost.final modifier is used to indicate t...
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Access Specifier
What will happen if same access specifier repeats more than once within a class?
Sarje
- Aug 17th, 2009
Multiple Acceess Specifier cannot be used with a class because it makes no sense and if you do so compile time error(wrong combination of modifiers) will be generated.
12srinu12
- Nov 7th, 2008
If the same access specifiers are used for the methods in the same class nothing will happen. Problem occurs only when all the classes in the program are assigned with same access specifiers.
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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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Null keyword
Is null a keyword? if not what is it?
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interviewprep9- Member Since Jun-2008 | Jun 14th, 2008
Capital N, Null is not a keyword or a reserved word.
All small letters, null is not a keyword either. but, it's a reserved word. you cannot use null as follows:
String null = "a";
null means that a reference is not pointing to any object.
Sarje
- Aug 17th, 2009
Null is not a keyword but null is reserved literal. null is the default value for instance variable.String str = null;means instance variable str does not hold reference of any object.
varmasuman
- Sep 13th, 2008
Null?means showing nothingWhenever one object reference refers null i.e? ServletConfig application=null;Then there is nothing in the object reference application.
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What is the difference between an object and an instance? And give me a real time example to differentiate these two?
Sarje
- Aug 15th, 2009
object and instance both are sameI think you want know the difference between reference and object.If so thenreference of any class type is a variable that can hold the reference(more or less we can s...
pravinsharma
- Oct 15th, 2008
An object is part of a process/thread which demands processor time through the JVM.The act of creating the object from a class is called instantiation.In literary sense an instance is existance/occurrence of an object.In this case a duplicate copy(instance) of an object is still the same object.
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Transient and Volatile.
What is the difference between Transient and Volatile. Does volatile variable is serialized and synchronised.
Sarje
- Aug 14th, 2009
Transient State of an object can be saved (write to any file) if the class implements java.io.Serializable interface. In this case all of the field's value will be saved. If we want any of the fie...
atmarammuduli
- Jun 17th, 2008
Volatile:Threads dont cache method copy of Volatile instance variables. Each time when the var is used the thread gets latest copy.Transient:instance var not serialized ever. After deserialization its value is null(object) or zero(primitive type).
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Usage of Abstract class and Interfaces
In Real time when we go for Abstract classes and when we go for Interfaces
Sarje
- Aug 13th, 2009
If you want to create only abstract methods in a class then use interface and if you want to create some of the methods as abstract and some as concrete then use abstract class.
dyy123
- Nov 14th, 2008
When you don't want to expose the implementation of the methods then you can use the Interface. Abstract class is will have some methods implemented and some unimplemented.
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Static data member
What is the use of static data member?
Sarje
- Aug 13th, 2009
Static data members field (variable) and method belong to class. Static fields can be used before creating an instance of the class and static method can be accessed using class name.
aditya_8584
- Mar 24th, 2009
Static data member has a class scope. A single copy of static data member get shared?within the objects of that class. A non-static member cannot access a static member of that class.
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(1)Can we have more than one connection object with database at same time?(2)Why Interfaces in JDBC have objects?
rammaheswara
- Aug 10th, 2009
Yes, we can have morethan one connection object same time. This is how we implement connection pooling. Poole minimum and maximum numebr of connections.
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Why cant we compare two objects with ==,why we should use only .equals() for objects.
we can compare two Strings with (==) when we assign some string value to the String variable,but if we create an object to that strings and compare eachother we cant use(==) operator ,because we can compare only values with(==) operator but as Objects contains references to that variables we cant use(==) operator,hence .equals() is used on references and (==) is useed on values
geeksterrahul
- Jul 25th, 2009
== operator checks to see if two references are referring to the same location on memory.This is also called shallow comparison..equals checks to see if the two objects match each other. This is also known as deep comparison.
chandanareddy
- Jan 31st, 2006
Both == and equals() can be used to compare objects but in different aspects== is used to check whether the references are aliases.equals() is used to check for object value equality. equals() method...
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It is a saying that static methods in JAVA programs should be minimised. What is the reason for this? any problems arise or there is any performance measures to be looked into it.
geeksterrahul
- Jul 25th, 2009
One simple answer:Static(per class) members are created one instance/class loader/class instance. so they will reside until the class unloads(application closes).Meaning,they will stay during the life...
sunil kulyana
- Jul 21st, 2006
Static variables and classesIn Java, usually a class member (variable or method) is accessed in conjunction with an object of its class. In the case of static variables and methods, it is possible to ...
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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 are the differences between C++ and Java
meSubhadip
- Jul 20th, 2009
The main differences are:?Java does not support typedefs, defines, or a preprocessorJava supports classes, but does not support structures or unionsJava does not support multiple inheritanceJava does...
lalitsonawane27
- Feb 7th, 2009
C++ is not a platform independent language while Java is platform independent language.
Core Java Interview Questions
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