Adv Java
Programming

1. What Is the Java Technology 2. Points to keep in mind for pyramid. 3. Java Pyramid Program on type 1 4. Java Pyramid Program on type 2 5. Java Pyramid Programs on Type 3 6. Java Pyramid Programs on type 4 7. Java Pyramid Programs on type 5 8. Classes and Objects 9. Recursive functions 10. Constructors in Java 11. Method Overloading 12. Constructor Overloading 13. Inheritance in Java 14. Interface in Java 15. Method Overriding and Hiding Method 16. The final keyword 17. Exception Handling 18. Properties, System & Runtime Class in Java 19. Building Java GUI 20. Layout Managers 21. Menu Bar 22. Applets 23. Threading 24. Java Netwoking 25. Programs for Science and Engineer 26. Prg to demonstrate pre and post increment 27. Prg to convert Farenheit to Celsius temperature 28. Prg to convert kilogram to different units 29. Prg to calculate surface area and volume of sphere 30. Prg to calculate frequency 31. Prg to determine co-ordinate points 32. Prg to determine Equilateral, Isosceles or Scalene triangle 33. Prg to demonstrate conditional operator 34. Prg to calculate Final and initial interest amount 35. Prg to separate entered number 36. Prg to examine while loops and conditions 37. Prg to calculate number of year 38. Prg to find Armstrong number or not 39. Prg to find all Armstrong number 40. Prg to find limited Armstrong number 41. Prg to find Armstrong number using user defined function 42. Prg to find frequency of student 43. Prg to find maximum and minimum number 44. Prg to print number triangle 45. Prg to print vertical number triangle 46. Prg to print number triangle 47. Prg to print binary right angle triangle 48. Prg to print * triangle 49. Prg to to print rhombus 50. Prg to print entered number triangle 51. Prg to to find nCr and nPr 52. Prg to enter an element in array 53. Prg to sort number using array 54. Prg to find the position of element in array 55. Prg to find the position of element in array using boolean flag 56. Prg to add one extra element in an array 57. Prg to find the equation of line 58. Prg to find the common element from two array 59. Prg to find the highest scorer 60. Prg to create a square of number 61. Prg to create Pascal triangle 62. Prg to subtraction, multiplication and division using methods and classes 63. Prg to determine salary grade 64. Prg for complex number 65. Prg to calculate area 66. Prg for Greatest Common Divisior 67. Prg for displaying studenta mark sheet 68. Prg for demonstrating inheritance 69. Prg to calculate area of triangle 70. Prg for calculating volume of sphere or hemisphere 71. Prg for demonstrate classes 72. Prg for employee details 73. Prg for demonstrating super and base class 74. Prg for Bank Account 75. Prg for professor and student details 76. Prg for Addition, Multiplication and finding Transpose of two matrix 77. Prg for counting number of words in a string 78. Prg to count number of vowels and consonants in a string 79. Prg to fine number of upper case, lower case, white spaces and digit in a string 80. Prg to fine number of upper case, lower case, white spaces and digit in a string without inbuilt function 81. Prg to arrange a string in alphabetic order 82. Prg to count the number of character occurrence in a string 83. Prg to find the string length and character position 84. Prg for converting first character of word into upper case 85. Prg for demonstrating vectors for manipulating records 86. Prg for manupulting items record using vectors 87. Prg for bank transaction 88. Prg for counting number of days between any two different date 89. Prg for exception handling 90. Prg for throwing exception 91. Prg for exception 92. Prg to throw exception when number is invalid 93. Prg for renaming the current thread 94. Prg for demonstrating strat method of thread 95. Prg to demonstrate sleep and and join method of thread 96. Prg to demonstrate yield method of thread 97. Prg for demonstrating thread in class inheritance 98. Threading program using runnable interface 99. Thread program using sleep 100. Java Applet program for creating fancy round eye 101. Java Applet program for creating fancy face 102. Java Applet program for drawing string 103. Java Applet program for creating fancy face 104. Java Applet program for displaying fancy fonts 105. Java Applet program for drawing and filling rectangle 106. Java Applet program for creating house 107. Java Applet program to show lifecycle of applet 108. Java Applet program for creating polygon 109. Java Applet program for creating rectangle 110. Java Applet program for drawing line 111. Java Applet program for getting applet width and height 112. Interview Question & Answer part 1 113. Interview Question & Answer part 2 114. Interview Question & Answer part 3 115. Interview Question & Answer part 4 116. Interview Question & Answer part 5 117. Interview Question & Answer part 6 118. Interview Question & Answer part 7 119. Interview Question & Answer part 8 120. Interview Question & Answer part 9 121. Interview Question & Answer part 10 122. Interview Question & Answer part 11
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JAVA Interview Questions and Answers Part 3

 

21. What is an Iterator?

  • Some of the collection classes provide traversal of their contents via a java.util.Iterator interface. This interface allows you to walk through a collection of objects, operating on each object in turn. Remember when using Iterators that they contain a snapshot of the collection at the time the Iterator was obtained; generally it is not advisable to modify the collection itself while traversing an Iterator.

 

22. State the significance of public, private, protected, default modifiers both singly and in combination and state the effect of package relationships on declared items qualified by these modifiers?

  • public :Public class is visible in other packages, field is visible everywhere (class must be public too)

  • private :Private variables or methods may be used only by an instance of the same class that declares the variable or method, A private feature may only be accessed by the class that owns the feature.

  • protected : Is available to all classes in the same package and also available to all subclasses of the class that owns the protected feature.This access is provided even to subclasses that reside in a different package from the class that owns the protected feature.

  • default :What you get by default ie, without any access modifier (ie, public private or protected).It means that it is visible to all within a particular package.

 

23. What is an abstract class?

  • Abstract class must be extended/subclassed (to be useful). It serves as a template. A class that is abstract may not be instantiated (ie, you may not call its constructor), abstract class may contain static data. Any class with an abstract method is automatically abstract itself, and must be declared as such.

  • A class may be declared abstract even if it has no abstract methods. This prevents it from being instantiated.

 

24. What is static in java?

  • Static means one per class, not one for each object no matter how many instance of a class might exist. This means that you can use them without creating an instance of a class.Static methods are implicitly final, because overriding is done based on the type of the object, and static methods are attached to a class, not an object. A static method in a superclass can be shadowed by another static method in a subclass, as long as the original method was not declared final. However, you can't override a static

  • Method with a nonstatic method. In other words, you can't change a static method into an instance method in a subclass.

 

25. Are the imports checked for validity at compile time? e.g. will the code containing an import such as java.lang.ABCD compile?

  • Yes the imports are checked for the semantic validity at compile time. The code containing above line of import will not compile. It will throw an error saying,can not resolve symbol

    1. symbol : class ABCD

    2. location: package io

    3. import java.io.ABCD;

 

26. Does importing a package imports them subpackages as well? e.g. Does importing com.MyTest.* also import com.MyTest.UnitTests.*?

  • No you will have to import the subpackages explicitly. Importing com.MyTest.* will import classes in the package MyTest only. It will not import any class in any of it's subpackage.

 

27. What is the difference between declaring a variable and defining a variable?

  • In declaration we just mention the type of the variable and it's name. We do not initialize it.

  • But defining means declaration+ initialization.

    1. e.g String s; is just a declaration while String s = new String ("abcd");

    2. Or String s = "abcd"; are both definitions.

28. What is the default value of an object reference declared as an instance variable?

  • null unless we define it explicitly.

 

29. Can a top level class be private or protected?

  • No. A top level class can not be private or protected. It can have either "public" or no modifier. If it does not have a modifier it is supposed to have a default access.

  • If a top level class is declared as private the compiler will complain that the "modifier private is not allowed here". This means that a top level class can not be private. Same is the case with protected.

 

30. What type of parameter passing does Java support?

  • In Java the arguments are always passed by value.

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