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 4

 

31. Primitive data types are passed by reference or pass by value?

  • Primitive data types are passed by value.

 

32. Objects are passed by value or by reference?

  • Java only supports pass by value. With objects,the object reference itself is passed by value and so both the original reference and parameter copy both refer to the same object.

 

33. What is serialization?

  • Serialization is a mechanism by which you can save the state of an object by converting it to a byte stream.

 

34. Which methods of Serializable interface should I implement?

  • The serializable interface is an empty interface,it does not contain any methods. So we do not implement any methods.

 

35. How can I customize the seralization process? i.e. how can one have a control over the serialization process?

  • Yes it is possible to have control over serialization process. The class should implement Externalizable interface. This interface contains two methods namely readExternal and writeExternal. You should implement these methods and write the logic for customizing the serialization process.

 

36. What is the common usage of serialization?

  • Whenever an object is to be sent over the network, objects need to be serialized. Moreover if the state of an object is to be saved, objects need to be serilazed.

 

37. What is Externalizable interface?

  • Externalizable is an interface which contains two methods readExternal and writeExternal.These methods give you a control over the serialization mechanism. Thus if your class implements this interface, you can customize the serialization process by implementing these methods.

 

38. Does Java provide any construct to find out the size of an object?

  • No there is not sizeof operator in Java. So there is not direct way to determine the size of an object directly in Java.

 

39. Give a simplest way to find out the time a method takes for execution without using any profiling tool?

  • Read the system time just before the method is invoked and immediately after method returns. Take the time difference, which will give you the time taken by a method for execution.

  • To put it in code...

long start = System.currentTimeMillis ();

method ();

long end = System.currentTimeMillis ();

System.out.println ("Time taken for execution is " +(end-start));

 

  • Remember that if the time taken for execution is too small, it might show that it is taking zero milliseconds for execution. Try it on a method which is big enough, in the sense the one which is doing considerable amout of processing.

 

40. What are wrapper classes?

  • Java provides specialized classes corresponding to each of the primitive data types. These are called wrapper classes. They are e.g. Integer, Character, Double etc.

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