Download Online Java Important Interview Questions

Java Important Interview Questions

1. Java’s which system allows a thread to enter a synchronized method on an object, and then wait there until some other thread explicitly notifies it to come out
Answer: Messaging

2. Packages act as containers for
Answer: Classes, Subordinate packages

3. Threads priorities are not integers that specify the relative priority of one thread to another.
Answer: False

4. When java program starts up, which thread begins running immediately?
Answer: Main thread

5. Java provides built-in support for which programming?
Answer: Multithreaded

6. The ________ is similar to break, except that instead of halting the execution of the loop, it starts the next iteration.
Answer: Continue

7. When can a constructor be called without specifying arguments?
Answer: When there are no constructors for the class

8. The mechanism which binds together the code and data and keeps both safe is ________.
Answer: Encapsulation

9. ________ is an instance of a class that implements the runnable interface.
Answer: thread

10. Expression must be of the data types :-
Answer: Byte , Short , Int

11. Java define eight simple types of data byte, short, int, long, char, float, double, boolean.
Answer: True

12. What modifiers may be used with top-level class?
Answer: Public , Abstract , Final

13. Syntax to declare a variable in java is :-
Answer: type identifier [=value][,identifier[=value]…]

14. ________ statement in java is conditional branch statement.
Answer: If

15. Which statement used inside a set of nested loops, will only break out of the innermost loop?
Answer: Break

16. In ________ statement condition is true, then statement 1 is executed.
Answer: If

17. The source for the frist package defines three classes
Answer: Protection , Derived , SamePackage

18. Java compiler stores the .class files in the path specified in CLASSPATH environmental variable.
Answer: False

19. Interface can be extended.
Answer: True

20. ________ is the logical construct upon which the entire java language is built.
Answer: Class

21. Is it necessary to implement all the methods of an interface while implementing the interface
Answer: False

22. Which loops can be nested in java?
Answer: While, Do-while, For

23. Float data type is useful when we need fractional values.
Answer: True

24. What all the run( ) method can do?
Answer: Can call other method, Declare variable

25. Variable in an interface are implicitly final and static.
Answer: True

26. Which of the following operators are used in conjunction with the this and super references?
Answer: The dot operator

27. The ________ keyword halts the execution of the current loop and forces control out of the loop.
Answer: Break

28.What is a data structure that controls the state of a collection of threads as a whole?
Answer: Thread group

29. By Providing the interface keyword, Java allows you to fully utilize the which aspect of polymorphism?
Answer: One interface, Multiple methods

30. For externalizable objects the ________ is solely responsible for the external format of its contents.
Answer: Class

31. Which are the java’s control statements?
Answer: For , If , Switch

32. What are the kinds of variables in Java?
Answer: Instance, local, class variables

33. Java Operators can be divided into these groups :-
Answer: Arithmetic , Bitwise , Relational

34. What is an array?
Answer: It is value collection of same type of data type

35. Modulus operator % can be applied to these data types :-
Answer: floating Point , Integer , Character

36. Start( )executes a call to ________.
Answer: run( )

37. ________ is an instance of the class.
Answer: Object

38. ________method starts a threrad by calling its run method.
Answer: start( )