1. What is the most important feature of
Java?
Java is a platform independent language.
2. What do you mean by platform
independence?
Platform independence means that we can
write and compile the java code in one
platform (eg Windows) and can execute the
class in any other supported platform eg
(Linux,Solaris,etc).
3. What is a JVM?
JVM is Java Virtual Machine which is a run
time environment for the compiled java class
files.
4. Are JVM's platform independent?
JVM's are not platform independent. JVM's are
platform specific run time implementation
provided by the vendor.
5. What is the difference between a JDK
and a JVM?
,JDK is Java Development Kit which is for
development purpose and it includes
execution environment also. But JVM is purely
a run time environment and hence you will
not be able to compile your source files using
a JVM.
6. What is a pointer and does Java
support pointers?
Pointer is a reference handle to a memory
location. Improper handling of pointers leads
to memory leaks and reliability issues hence
Java doesn't support the usage of pointers.
7. What is the base class of all classes?
java.lang.Object
8. Does Java support multiple
inheritance?
Java doesn't support multiple inheritance.
9. Is Java a pure object oriented
language?
Java uses primitive data types and hence is
not a pure object oriented language.
,10. Are arrays primitive data types?
In Java, Arrays are objects.
11. What is difference between Path and
Classpath?
Path and Classpath are operating system level
environment variales. Path is used define
where the system can find the
executables(.exe) files and classpath is used
to specify the location .class files.
12. What are local variables?
Local varaiables are those which are declared
within a block of code like methods. Local
variables should be initialised before
accessing them.
13. What are instance variables?
Instance variables are those which are
defined at the class level. Instance variables
need not be initialized before using them as
they are automatically initialized to their
default values.
14. How to define a constant variable in
Java?
, The variable should be declared
as static and final. So only one copy of the
variable exists for all instances of the class
and the value can't be changed also.
static final int PI = 2.14; is an
example for constant.
15. Should a main() method be
compulsorily declared in all java classes?
No not required. main() method should be
defined only if the source class is a java
application.
16. What is the return type of the main()
method?
Main() method doesn't return anything hence
declared void.
17. Why is the main() method declared
static?
main() method is called by the JVM even
before the instantiation of the class hence it is
declared as static.
18. What is the arguement of main()
method?
Java?
Java is a platform independent language.
2. What do you mean by platform
independence?
Platform independence means that we can
write and compile the java code in one
platform (eg Windows) and can execute the
class in any other supported platform eg
(Linux,Solaris,etc).
3. What is a JVM?
JVM is Java Virtual Machine which is a run
time environment for the compiled java class
files.
4. Are JVM's platform independent?
JVM's are not platform independent. JVM's are
platform specific run time implementation
provided by the vendor.
5. What is the difference between a JDK
and a JVM?
,JDK is Java Development Kit which is for
development purpose and it includes
execution environment also. But JVM is purely
a run time environment and hence you will
not be able to compile your source files using
a JVM.
6. What is a pointer and does Java
support pointers?
Pointer is a reference handle to a memory
location. Improper handling of pointers leads
to memory leaks and reliability issues hence
Java doesn't support the usage of pointers.
7. What is the base class of all classes?
java.lang.Object
8. Does Java support multiple
inheritance?
Java doesn't support multiple inheritance.
9. Is Java a pure object oriented
language?
Java uses primitive data types and hence is
not a pure object oriented language.
,10. Are arrays primitive data types?
In Java, Arrays are objects.
11. What is difference between Path and
Classpath?
Path and Classpath are operating system level
environment variales. Path is used define
where the system can find the
executables(.exe) files and classpath is used
to specify the location .class files.
12. What are local variables?
Local varaiables are those which are declared
within a block of code like methods. Local
variables should be initialised before
accessing them.
13. What are instance variables?
Instance variables are those which are
defined at the class level. Instance variables
need not be initialized before using them as
they are automatically initialized to their
default values.
14. How to define a constant variable in
Java?
, The variable should be declared
as static and final. So only one copy of the
variable exists for all instances of the class
and the value can't be changed also.
static final int PI = 2.14; is an
example for constant.
15. Should a main() method be
compulsorily declared in all java classes?
No not required. main() method should be
defined only if the source class is a java
application.
16. What is the return type of the main()
method?
Main() method doesn't return anything hence
declared void.
17. Why is the main() method declared
static?
main() method is called by the JVM even
before the instantiation of the class hence it is
declared as static.
18. What is the arguement of main()
method?
