Ericsson Java Questions: Introduction to Classes and Methods

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  1. Which is used to get the value of the instance variables? Ans: Dot notation.

  2. The new operator creates a single instance named class and returns a reference to that object.

  3. A class is a template for multiple objects with similar features.

  4. What is mean by garbage collection? Ans: When an object is no longer referred to by any variable, Java automatically reclaims memory used by that object. This is known as garbage collection.

  5. What are methods and how are they defined? Ans: Methods are functions that operate on instances of classes in which they are defined. Objects can communicate with each other using methods and can call methods in other classes. Method definition has four parts. They are name of the method, type of object or primitive type the method returns, a list of parameters and the body of the method. A method's signature is a combination of the first three parts mentioned above:

  6. What is calling method? Ans: Calling methods are similar to calling or referring to an instance variable. These methods are accessed using dot notation. Ex: Obj. Methodname (param1, param2)

  7. Which method is used to determine the class of an object? Ans: GetClass () method can be used to find out what class the belongs to. This class is defined in the object class and is available to all objects.

  8. All the classes in java. Lang package are automatically imported when a program is compiled.

  9. How can class be imported to a program? Ans: To import a class, the import keyword should be used as shown. import classname

  10. How can class be imported from a package to a program? Ans: Import java. Packagename. Classname (or) import java. Package name. *

  11. What is a constructor? Ans: A constructor is a special kind of method that determines how an object is initialized when created.

  12. Which keyword is used to create an instance of a class? Ans: New.

  13. Which method is used to garbage collect an object? Ans: Finalize ().

  14. Constructors can be overloaded like regular methods.

  15. What is casting? Ans: Casting is bused to convert the value of one type to another.

  16. Casting between primitive types allows conversion of one primitive type to another.

  17. Casting occurs commonly between numeric types.

  18. Boolean values can be cast into any other primitive type.

  19. Casting does not affect the original object or value.

  20. Which cast must be used to convert a larger value into a smaller one? Ans: Explicit cast.

  21. Which cast must be used to cast an object to another class? Ans: Specific cast.

  22. Which of the following features are common to both Java & C + +?

  23. Which of the following statements accurately describe the use of access modifiers within a class definition?

  24. Suppose a given instance variable has been declared private. Can this instance variable be manipulated by methods out side its class?

  25. Which of the following statements can be used to describe a public method?

  26. Which of the following types of class members can be part of the internal part of a class?

  27. You would use the ____ operator to create a single instance of a named class.

  28. Which of the following statements correctly describes the relation between an object and the instance variable it stores?

  29. If no input parameters are specified in a method declaration then the declaration will include __.

  30. What are the functions of the dot (.) operator?

  31. Which of the following can be referenced by this variable?

  32. The this reference is used in conjunction with ___methods.

  33. Which of the following operators are used in conjunction with the this and super references?

  34. A constructor is automatically called when an object is instantiated

  35. When may a constructor be called without specifying arguments?

  36. Each class in java can have a finalizer method

  37. When an object is referenced, does this mean that it has been identified by the finalizer method for garbage collection?

  38. Because finalize () belongs to the java. Lang. Object class, it is present in all ___.

  39. Identify the true statements about finalization.

  40. When you write finalize () method for your class, you are overriding a finalizer inherited from a super class.

  41. Java memory management mechanism garbage collects objects which are no longer referenced

  42. are objects referenced by a variable candidates for garbage collection when the variable goes out of scope?

  43. Java's garbage collector runs as a ___ priority thread waiting for __priority threads to relinquish the processor.

  44. The garbage collector will run immediately when the system is out of memory

  45. You can explicitly drop a object reference by setting the value of a variable whose data type is a reference type to ___ Ans: Null

  46. When might your program wish to run the garbage collecter?

  47. For externalizable objects the class is solely responsible for the external format of its contents

  48. When an object is stored, are all of the objects that are reachable from that object stored as well?

  49. The default__ of objects protects private and trancient data, and supports the __ of the classes

  50. Which are keywords in Java?

  51. When must the main class and the file name coincide? Ans: When class is declared public.

  52. What are different modifiers? Ans: Public, private, protected, default, static, trancient, volatile, final, abstract.

  53. What are access modifiers? Ans: Public, private, protected, default.

  54. What is meant by “Passing by value” and “Passing by reference” Ans: Objects pass by referrence Methods-pass by value

  55. Is a class a subclass of itself? Ans: A class is a subclass itself.

  56. What modifiers may be used with top-level class? Ans: Public, abstract, final.

  57. What is an example of polymorphism?

Inner class

Anonymous classes

Method overloading

Method overriding

Ans: c