JAVA

1. Java-overview 2. Features of Java 3. History of Java 4. HW SW Req for Java SE 7 5. Java Environment Setup 6. Basic Requirement 7. Comments 8. My First Program in Java 9. Line Break 10. Escape Sequences 11. Literals in Java 12. Identifiers in Java 13. Variables in Java 14. Data-Types in Java 15. Declare Variables 16. Reserved Key Words 17. printf() 18. Chained & Embedded state 19. Prog.to print sum of 2 nos 20. Scanner class 21. Prg.to print sum & average 22. Area & Perimeter of Rectangle 23. Area Circumference of Circle 24. Prg.for Simple Calculator 25. Operatos in Java 26. Ex. Of Operators 27. Swap two numbers 28. Hierarchy of Operators 29. if( ) statement 30. Prg.to check +ve,-ve or zero 31. if..else statement 32. Prg.to check Odd or Even 33. Prg.to print larger of 2 nos 34. Prg.to print largest of 3 nos 35. Prg.to check divisibility 36. Prg.to check print range 37. for. . . loop statement 38. prg.to print series of nos 39. Prg.to check divisibility 40. prg.to print sum of nos 41. Prg.to print Pyramid 42. prg.for Factorial 43. prg.to fill screen 44. prg.for largest/smallest no 45. prg.to print reverse no 46. prg.to add each digit 47. prg.for sum of series 48. prg.for fibonacci series 49. prg.to check Prime nos 50. prg. Prime no from 1 to 100 51. prg.Specified Prime nos 52. while( ) statement 53. do. . While statement 54. break & continue statement 55. switch case statement 56. Array in Java 57. print reverse order using array 58. Ascending/Descending order 59. prg.to search no in Array 60. Multidimensional Array 61. String in Java 62. String with spaces 63. prg.to print string in reverse 64. prg. to count A,E,I,O,U vowel 65. User defined methods 66. Methods program example 67. General Purpose Programs 68. Loan & EMI calculation prg. 69. Table print prg. 70. Leap year program 71. lower to UPPER case prg. 72. Age Distribution prg. 73. Bank note calculation prg. 74. Simple Interest prg. 75. Compound Interest prg. 76. Simple Depreciation prg. 77. Reducing bal.Depreciation prg. 78. Marksheet prg. 79. Income Tax prg. 80. Time calculator prg. 81. Distance converter prg. 82. Volume Air Calculation prg. 83. Time to fill Water Tank prg. 84. Salary Calculation prg. 85. Total Sale Calculation prg. 86. Male/Female percentage prg. 87. Library Rent prg. 88. Office Expance prg. 89. Total Salary Calculation prg. 90. Profit or Loss prg. 91. Total Profit/Loss prg. 92. Palindrome program 93. Java Interview Part1 94. Java Interview Part2 95. Java Interview Part3 96. Java Interview Part4 97. Java Interview Part5 98. Java Interview Part6 99. Java Interview Part7 100. Java Interview Part8 101. Java Interview Part9 102. Java Interview Part10 103. Java Interview Part11
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JAVA Interview Questions and Answers Part 2

11. What is the difference between an Interface and an Abstract class?

  • An abstract class can have instance methods that implement a default behavior.

  • An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract.

  • An interface has all public members and no implementation.

  • An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.

 

12. What is the garbage collection in Java, and when is it used?

  • The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources can be reclaimed and reused.

  • A Java object is subject to garbage collection when it becomes unreachable to the program in which it is used.

 

13. Describe synchronization in respect to multithreading?

  • With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchonization, it is possible for one thread to modify a shared variable while another thread is in the process of using or updating same shared variable. This usually leads to significant errors.

 

14. Explain different way of using thread?

  • The thread could be implemented by using runnable interface or by inheriting from the Thread class. The former is more advantageous, 'cause when you are going for multiple inheritance..the only interface can help.

 

15. What are pass by reference and passby value?

  • Pass By Reference means the passing the address itself rather than passing the value. Passby Value means passing a copy of the value to be passed.

 

16. What is HashMap and Map?

  • Map is Interface and Hashmap is class that implements that.

  • Map: The features of Map interface are the elements should be stored in key/value pairs. Map accepts null values also both as key and value. Map does not accept duplicate keys (if added a duplicate, the earlier one is simply overridden and not a compilation error or exception). These features are inherited by HashMap.

  • The Map and the derived classes of Map are part of collections framework even though Map maintains its separate hierarchy. Map is best suitable to store the properties of a student like name and marks or telephone directory (name and telephone number). Map uses hashing algorithm to return the value when a key is supplied.

  • HashMap: is an implementation of Map. All the properties of Map, discussed earlier, are attained by HashMap. To have the advantage of performance, the HashMap object can be assigned explicitly with initial capacity and load factor.

  • The capacity gives the existing storage capability and the load factor gives increment rate of providing additional capacity when the existing capacity is exhausted.

 

17. Difference between HashMap and HashTable?

  • The HashMap class is roughly equivalent to Hashtable, except that it is unsynchronized and permits nulls. (HashMap allows null values as key and value whereas Hashtable doesnt allow).

  • HashMap does not guarantee that the order of the map will remain constant over time.

  • HashMap is unsynchronized and Hashtable is synchronized.

 

18. Difference between Vector and ArrayList?

  • Vector is synchronized whereas arraylist is not.

 

19. Difference between Swing and Awt?

  • AWT are heavy weight componenets. Swings are light weight components.Hence swing works faster than AWT

 

20. What is the difference between a constructor and a method?

  • A constructor is a member function of a class that is used to create objects of that class. It has the same name as the class itself, has no return type, and is invoked using the new operator.

  • A method is an ordinary member function of a class. It has its own name, a return type (which may be void), and is invoked using the dot operator.

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