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What is the Output of the following Java Program
public interface I1{Static String x="inside I1";public void someMethod();}class A implements I1{ public static void main(String args[[]){ System.out.println("Calling I1 var ..."+I1.x);}}
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abuthahir.d- Member Since Jan-2008 | Apr 14th, 2008
Compilation error due to 2 reasons.
1. All variables defined in the Interfaces are implicitly public static final. So need not specify "Static" in interface.
2. If any of the member functions of a Interface is not Overriden , a compilation error will be thrownshanu_rastogi
- Feb 3rd, 2010
It is right that you dont need to explicitly define a varible static but if you do so then it will not give compliler error..
sarojmohanty
- Nov 19th, 2009
Compilation error will come because you must have to override the abstract method of the implememted interface. After the implementation of the abstract method the program will compile and run properly and print "inside l1".
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What are the differences between weak reference, soft reference and phantom reference
uncer
- Jan 28th, 2010
The garbage collector might or might not reclaim a softly reachable object depending on how recently the object was created or accessed, but is required to clear all soft references before throwing an...
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Marker Interface
When there is no methods in the marker interface, then what is the use of marker interface. What is the functionality of the interface. Why do we need to implement marker interface?
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Saroj_mi2- Member Since Sep-2009 | Sep 14th, 2009
Marker interface is an interface with out having any implementation methods.
By implementing this interfaces, we will specify some special behaviour to implemented class.
Examples: Serializable, Cloneable
For example if we want to create a clone for a an object of class using clone()(clone()-- which is an object class method), then class need to implement Cloneable interface.
This mark is to JVM to handle the interface.If you are implimenting this interface the compliler will know some specific job need to be done.
For Cloneable interface even it does not have any methode the JVM looks for clone() method to execute. But the complier will not fail if the clone() meth is not implimented.
Narotam
- Jan 19th, 2010
Marker interface do not have any method. It is used only to inform JVM that?such class can do some special function like clone, serialize.
uncer
- Jan 15th, 2010
When you need to perform some behavioral function on any class without implementing method in implemented interface we implement an interface such interface called marker interface for exmple serializabe, cloneable.
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Whether private,protected method can be overloaded,overrided or not?Tell me reason?
uncer
- Jan 15th, 2010
A Private Protected Methods can be overloaded but in the concept of overriding access modifier should not be restrictedmean:If a method in superclass is public then overrided method in subclass must b...
Sarje
- Aug 12th, 2009
Private protected methods can be overloaded and overrided. But while overrding method following rules must be satisfied We can not narrow the accessibility but can be widen. Means if the access specif...
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Why java is not 100% oops
smartcasanova
- Jan 13th, 2010
Because of the promitive data types provided in the java such as int, char float, these primitives are not objects hence Java is not pure OO.
sahit
- Oct 27th, 2009
Java does not support multiple inheritance as well as operator overloading, so we can say that Java is not completly supporting OOPs.
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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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">
What is the meaning of "final" keyword?
sambitsahu
- Jan 5th, 2010
Final Variable :: ConstantFinal Method :: Can't OverrideFinal Class :: Can't instatiate
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How hashtable is synchronized?why hashmap is not synchronized?Can we make hashmap synchronized?
karthi1106
- Dec 10th, 2009
Vector/Hashtable Original classes before the introduction of Collections API. Vector & Hashtable are synchronized. Any method that touches their contents is thread-safe. ArrayList/HashMap So...
ssubhajit
- Nov 25th, 2009
Use the Code below to make a Hashmap synchronized ...Hashmap objHashmap = Collections.synchronizedMap(new HashMap(....));
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Why wait and notify method in Object class
Why wait and notify method in Object class, why these are not in Thread Class.
sujithkthomas
- Nov 13th, 2009
Inter thread communication is not directly supported?by the producer or consumer, but by the object they are acting upon. Also lock is associated with a particular object. If a thread needs a lock it use sync block and release using object's methods.
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Wrapping an Object
What does "wrapping" an object mean?
SreerangKulkarni
- Oct 29th, 2009
When an object A is said to "Wrap" object B, it means that Object A HAS A reference to the Object B and deligates calls to it.
karthik_knight2000
- Dec 3rd, 2008
Wrapping an object means we are covering that object, say for example? in Java we can say?String is a class as well as?String is a data type.String s;?? // here s is object of String class ???...
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Meaning - Abstract classes, abstract methods
jawaharl0207
- Oct 25th, 2009
Abstract Class: There are two ways to create abstract class, one is by mentioning abstract key before the class declaration, and second one is by mentioning abstract key before the method declaration ...
haruto
- Oct 22nd, 2009
In java a class has a well defined structure and behaviour. There are times where we do not need to implement a method such methods are written in the class where the class is preceded by keyw...
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I want to know output of this program and the flow alsopublic class Aquestion { private int i = giveMeJ(); private int j = 10; private int giveMeJ() { return j; } public static void main(String args[]) { System.out.println((new Aquestion()).i); } }
talktoatish
- Aug 16th, 2009
public class Foo { private static int j = 10; private static int i = giveMeJ(); private static int giveMeJ() { System.out.println("in the method" + i + j); return j; } public static void...
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1. Can You catch the Error? 2. Difference between compiletime exception and runtime exception?3. How you throw user defined exception?4. How you handle throwable while using exceptions ?5. What are the methods available in Object ?6. Is there any methods available in serialization ?7. How you seralize an Object ?8.How you get the serialized object ? 9. Any methods available in deseralization ?
rammaheswara
- Sep 29th, 2009
Yes, you can catch the Error as it is a subclass of Throwable, but you are not supposed to.For most of the errors like ( out of memry), there is no use of catching the error.MAHES
ambuj
- Jun 28th, 2007
No, because error is not related to ur progamming envirnment through which we can apply our exception handling mecanism. It?occurs only due to operating system failure, System virus affected etc.
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How We Can We write our own exceptions?
maddy_me
- Sep 22nd, 2009
we can write our own exceptions by extending them either from Throwable or from Exception.class Example1{ public static void main(String[] args) throws MyException { ...
d
- Mar 9th, 2006
To write our own Exception class1)Our class must be subclass of Throwable or Exception class2)Evert Exception class provide 2 constructors a) no arguments b) one argument i.e String argument3) Optional: Overidding toString metod of java.lang.Object
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Convert string object to primitive Integer Type
How can i convert a string object to a primitive Integer type???????Thanks
maddy_me
- Sep 18th, 2009
class StringConver{ public static void main(String[] s) { //String s1 = "Hello"; If you try this you will get NumberFormatException ...
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What does the state consists of for an Object which has to be serialized?
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Marker interface having no methods right.. then what is the use of marker interface? for what purpose we use marker interface?
Ravi.Hingarajiya
- Aug 27th, 2009
It is used to identify class. In the read project, there are so many classes. It can identify that which class belongs to which module Exmaple : Cloneable interface can be cloned. The Java compi...
amitabh26d
- Aug 26th, 2009
Marked interfaces is for compiler use and we need not have to worry about its implementation.? Yes it does not have any methods, it is because by implementing marked interfaces we are telling a compiler?that it can optimise this class as per the specification of Java for that interfaces.
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SetEx setEx1 = new SetEx("Java");
String str1 = new String("Java");
String str2 = new String("Java");
s.add(setEx);
s.add(setEx1);
s.add(str1);
s.add(str2);
System.out.println("No Of elements in the Set is " + s.size());
}
What is the result and how?">Import java.util.*;public class SetEx { private String str; SetEx(String s) { str = s } public static void main(String[] ar) { Set s = new HashSet(); SetEx setEx = new SetEx("Java"); SetEx setEx1 = new SetEx("Java"); String str1 = new String("Java"); String str2 = new String("Java"); s.add(setEx); s.add(setEx1); s.add(str1); s.add(str2); System.out.println("No Of elements in the Set is " + s.size()); }What is the result and how?
james.vinett
- Aug 24th, 2009
The result is 3 even though you would want it to be 2.You MUST override equals() and hashCode() for proper use of add in HashSet.
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What is "JIT ENGINE" in Java?
james.vinett
- Aug 24th, 2009
The just-in-time compiler compiles byte code into native machine language when it first encounters it and then reuses that compiled code rather than recompiling it again. This give performance gains over the interpreter model which interprets the byte code every time it encounters it.
sampra
- Feb 14th, 2008
jit reads the whole byte code and exceute once where as interpretaor does it by line by line
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What is the difference between instance,object,refference,class.
Give the answer
Sarje
- Aug 19th, 2009
Class : A class is category of the object (any real entity) and acts as blueprint to create such object.For example if you want to develop an application for any company then its employee will be yo...
priya
- Dec 25th, 2005
Class : A class is a user defined data type with set of data members & member functionsObject : An Object is an instance of a classReference : A reference is just like a pointer pointing to an objectInstance :This represents the values of data members of a class at a particular time
Core Java Interview Questions
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