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Java Interview Questions on Package and Interface

>> Wednesday, September 29, 2010

Interview Questions on Package and interface in Java

1) What are packages ? What is use of packages ?

Ans :The package statement defines a name space in which classes are stored.If you omit the package, the classes are put into the default package.
Signature... package pkg;
Use: * It specifies to which package the classes defined in a file belongs to. * Package is both naming and a visibility control mechanism.

2) What is difference between importing "java.applet.Applet" and "java.applet.*;" ?

Ans :"java.applet.Applet" will import only the class Applet from the package java.applet
Where as "java.applet.*" will import all the classes from java.applet package.

3) What do you understand by package access specifier?

Ans : public: Anything declared as public can be accessed from anywhere
private: Anything declared in the private can’t be seen outside of its class.
default: It is visible to subclasses as well as to other classes in the same package.

4) What is interface? What is use of interface?

Ans : It is similar to class which may contain method’s signature only but not bodies.
Methods declared in interface are abstract methods. We can implement many interfaces on a class which support the multiple inheritance.

5) Is it is necessary to implement all methods in an interface?

Ans : Yes. All the methods have to be implemented.

6) Which is the default access modifier for an interface method?

Ans : public.

7) Can we define a variable in an interface ?and what type it should be ?

Ans : Yes we can define a variable in an interface. They are implicitly final and static.

8) What is difference between interface and an abstract class?

Ans : All the methods declared inside an Interface are abstract. Where as abstract class must have at least one abstract method and others may be concrete or abstract.
In Interface we need not use the keyword abstract for the methods.

9) By default, all program import the java.lang package.

True/False

Ans : True

10) Java compiler stores the .class files in the path specified in CLASSPATH environmental variable.

True/False

Ans : False


11) User-defined package can also be imported just like the standard packages.

True/False

Ans : True

12) When a program does not want to handle exception, the ______class is used.

Ans : Throws

13) The main subclass of the Exception class is _______ class.

Ans : RuntimeException

14) Only subclasses of ______class may be caught or thrown.

Ans : Throwable

15) Any user-defined exception class is a subclass of the _____ class.

Ans : Exception

16) The catch clause of the user-defined exception class should ______ its Base class catch clause.

Ans : Exception

17) A _______ is used to separate the hierarchy of the class while declaring an Import statement.

Ans : Package

18) All standard classes of Java are included within a package called _____.
Ans : java.lang

19) All the classes in a package can be simultaneously imported using ____.

Ans : *

20) Can you define a variable inside an Interface. If no, why? If yes, how?

Ans.: YES. final and static

21) How many concrete classes can you have inside an interface?

Ans.: None

22) Can you extend an interface?

Ans.: Yes

23) Is it necessary to implement all the methods of an interface while implementing the interface?

Ans.: No

24) If you do not implement all the methods of an interface while implementing , what specifier should you use for the class ?

Ans.: abstract

25) How do you achieve multiple inheritance in Java?

Ans: Using interfaces.

26) How to declare an interface example?

Ans : access class classname implements interface.

27) Can you achieve multiple interface through interface?

a)True
b) false

Ans : a.

28) Can variables be declared in an interface ? If so, what are the modifiers?

Ans : Yes. final and static are the modifiers can be declared in an interface.

29) What are the possible access modifiers when implementing interface methods?

Ans : public.

30) Can anonymous classes be implemented an interface?

Ans : Yes.

31) Interfaces can’t be extended.

a)True

b)False

Ans : b.

32) Is it possible to use few methods of an interface in a class ? If so, how?

Ans : Yes. Declare the class as abstract.

SCJP 5.0 meterials and ebooks Download

>> Saturday, September 18, 2010

SCJP Certification of Srikanth Pagada_JavabynataraJ

Hello friends,

I have the materials of Scjp 4.0,Scjp 5.0 ebooks .I like to share with you guys. I am giving the links of these two scjp books in a zip file format.It contains 17 or 18 chapters with those two books.

These books are enough to prepare the scjp certification.But you should be very careful and understand what you are reading.

Ok.Guys All the Best.

Download here Scjp 4.0

Download here Scjp 5.0
Reference Books:

Java Interview Questions by Nageswara Rao

>> Friday, September 10, 2010

The famous java lecturer Nageswara Rao from InetSolv Ameerpeta, Hyderabad has written java interview Questions. Also he written several books on Core Java and J2EE technologies.
You may be an experienced Java developer with hand on experience in core development or you may be a fresher who is looking for an entry in java job market, if you want to hit the job market , you may need to refresh some of the basic java terms or you may need to know what are the commonly asked questions to prepare yourself to for java technical interview.
Java interview Questions-JavabynataraJYou as an experienced java developer, just need to refresh your knowledge on java. But you as a fresher may need to know what can be the possible questions , what are the commonly asked questions, what are the valid answers for these questions and so on.

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