JAVA Interview Questions With Answers
1. What is the most important feature of Java?
3. What is a JVM?
4. Are JVM's platform independent?
5. What is the difference between a JDK and a JVM?
6. What is a pointer and does Java support pointers?
7. What is the base class of all classes?
12. What are local variables?
13. What are instance variables?
14. How to define a constant variable in Java?
16. What is the return type of the main() method?
18. What is the arguement of main() method?
20. Can a main() method be declared final?
23. What is a package?
24. Which package is imported by default?
28. What is the purpose of declaring a variable as final?
29. What is the impact of declaring a method as final?
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).
JVM is Java Virtual Machine which is a run time environment for the compiled java class files.
JVM's are not platform independent. JVM's are platform specific run time implementation provided by the vendor.
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.
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.
java.lang.Object8. 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 Class path?
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.
Local varaiables are those which are declared within a block of code like methods. Local variables should be initialised before accessing them.
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.
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.
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.
Main() method accepts an array of String object as arguement.19. Can a main() method be overloaded?
Yes. You can have any number of main() methods with different method signature and implementation in the class.
Yes. Any inheriting class will not be able to have it's own default main() method.21. Does the order of public and static declaration matter in main() method?
No. It doesn't matter but void should always come before main().22. Can a source file contain more than one class declaration?
Yes a single source file can contain any number of Class declarations but only one of the class can be declared as public.
Package is a collection of related classes and interfaces. package declaration should be first statement in a java class.
java.lang package is imported by default even without a package declaration.
Core Java - Interview Questions and Answers
@ : Home > Technical Interview > Core Java > Interview Questions25. Can a class declared as private be accessed outside it's package?
Not possible.26. Can a class be declared as protected?
A class can't be declared as protected. only methods can be declared as protected.27. What is the access scope of a protected method?
A protected method can be accessed by the classes within the same package or by the subclasses of the class in any package.
A final variable's value can't be changed. final variables should be initialized before using them.
A method declared as final can't be overridden. A sub-class can't have the same method signature with a different implementation.30. I don't want my class to be inherited by any other class. What should i do?
You should declared your class as final. But you can't define your class as final, if it is an abstract class. A class declared as final can't be extended by any other class.
