Java Interview Questions

Java Interview Questions

1.       How to declare the variable as constant in core java finally keyword.?

2.       How  to display the even numbers?

3.       How to check whether the given number is prime or not?

4.       Display the first 10 Fibonacci number.

5.       What is the difference between static method and instance method?

6.       Find the factorial of a number by using recursive method.

7.       What is the difference between method overloading and method overriding?

8.       Can we overload main method?

9.       What is the difference between JDK, JRE and JVM?

10.   Difference between Abstract class and interface class?

11.   Can we declare methods without using abstract keyword within the abstract class?

12.   What is immutable method?

13.   Difference between constructor and method?

14.   Can we apply overloading concept on constructor? Give an eg.

15.   What is the use of  ‘this’  keyword?

16.   What is the use of super keyword in a sub-class?

17.   Difference between Call by value and call by reference. Given an eg for each.

18.   How to make a particular method as immutable?

19.   Difference between checked and unchecked exceptions.

20.   Difference between catch block and final block.

21.   Difference between throw and throws.

22.   How to create the nested directories?

23.   How to read all the recursive directories in a particular directory or drive?

24.   Assume there is a directory. The directory having ‘n’ number of subdirectory and file(.txt, .xlsx, .csv). write a program to delete only the excel file

a)within the current directory

             b)within all sub directory.

25.   What is string tokenizer? How to split the string?

26.   How to split a particular string by using pattern clause(regular expression)?

27.   Write the regular expression for date.

28.   Write the regular expression for 24hurs or 12 hours time format.

29.   Write the regular expression for IP address.

30.   Write the regular expression for annogram. The given string is GOD, verify all the possible anagrams.?

31.   The given string is “ software Testing training”  find out necessary times the ‘t’ ‘s’ ‘a’ as repeated?

32.   The given string is  “programming” reverse it without using reverse.

33.   Difference between ArrayList and LinkedList.

34.   Difference between HashSet and TreeSet.

35.   Difference between Hashmap,Treemap and Hashtable.

36.   How to read the elements which are stored in hashmap, hashset by using iterator object.

37.   Create a text file and write the content to a text file in a separate line?

38.   Read the content of text file each line wise?

39.   Give an example for access specfier protected, public, default and private modifier?

40.   By using java program approach explain the stack(pop &push) approach?

41.   Give an example run time polymorphism?

42.   In a linear Inheritance how the execution of the constructor taking place? What is constructor Channing?

43.   What is Reflection keyword in the java?

44.   How to read the excel file values?

45.   Verify the given string is palindrome or not?

46.   Find out the missing number(assume numbers 1-10 those are 1,4,5,7,9,10)?

47.   How to convert multiple inheritance in a java?

48.   A subclass can extend super class and interface simultaneously?

49.   A Sub class can extend to super class simultaneously?

50.   Can we declare any instance variable in interface?

51.   Can we declare the constructor as final?

52.   On which factor method overloading can we decide?

53.   By using interface Reference can we create the object for the class give an example?

54.   Assume Interface is having ten methods there is one subclass it is implementing only five methods and same class has its own three methods?

A ) Create the object for class?

b) Create the object with respect to interface and execute?

55.   Can we able to create the object for the abstract class?

56.   What is abstract class?

57.   What is casting?

58.   Fetch the value from the database by using core java?

59.   Insert  the records into the database by using core java?

60.   Can we read the metadata of the database?

61.   Give an example for calendar class?

62.   Give an example for Date format & SimpleDate format?

63.   Write a method if you pass  80 it has to return 40 and if you pass 40 it has to return 80?

64.   What is garbage collection?

65.   Can we pass object as parameter to the method ? give an example?

66.   Can we written object from a method?

67.   What is inner class?

68.   Write a program to multiplication of matrix?

69.   How to assign elements to single dimensional array & two dimensional array?

70.   How to find out the no of elements stored in a Array?

71.   How to find out the no of characters string?

72.   How to find out the no of Elements stored in arraylist & linked list?

73.   How to read Property values from the property file?

74.   Write values to property file?

75.   How to copy the files from one directory to another directory?

76.   If there are string values, date value, numeric ,blank values are available excel file, how to read  this?

77.   There is a paragraph it is containing n number of time “technology” is repeated.  find how many times it was repeated (by using regular expression).

78.   What is difference between exception and throwable?

79.   In a multiple catch statements in single try statement can we use multiple catch statements?

a)In a multiple catch statement the first catch is exception? Does it work?

b)In a multiple catch statement last catch contain class.

80.   Can we use nested try statement ? give an example.

81.   How to generate the random number in core java?

82.   What is Object oriented programming and Object Based programming?

83.   How to pass command line arguments in core java?

84.   How to import a particular package?

85.   Display the stars in Equilateral triangle?

86.   Display the stars in Diamond ,triangle, rectangle shape ?

87.   What is difference between break and continue? give an example.

88.   Give an example for the ‘toString’ ?

89.   Read the Key and values in the Hashmap and treemap?

90.   What is difference between Enumeration and Iteration?

91.   What is difference between iterator and listiterator?

92.   By using Excel program, whether the given sheet is available or not.

93.   By using Excel programming write a method if you pass the column number and row number it has specify the value.

94.   How to write a value to specific column number?

95.   Write a program to delete the particular sheet?

96.   Write a program to add the particular sheet?

97.   Read the values from Database table of third column and write to a excel sheet?

98.   Read only the last record from the database table?

99.   In a single source file can we able to create to public classes or not?