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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Variables in Java tutorials

  • Variable are placeholder to store values.

  • As value varies from time to time, it is called variable.

  • Variable names are name given to location in memory. Those memory locations can contain integer, real or character data.

  • Every variable is identified by a unique name.

  • As Java being, case sensitive, variable Age is different that variable age.

Syntax:

The syntax for variable declaration in Java is below:

<datatype><variable_list>=<value>;

  • Here, data_type must be a valid Java data type including char, int, float, double, or any user defined data type etc, and variable_list may consist of one or more identifier names separated by commas.

  • Note: Datatype is explained in next topic of this course.

Variable Naming rules in Java

  • Variable must start with letter or underscore(_), which may be followed by a sequence of letters or digits(0-9).

  • The first character in a variable name cannot be a digit.

  • Variable in Java can have any number of character.

  • Variable name must be unique.

  • Example: To store five different numbers, five unique variable names need to be used.

  • Special Characters are not allowed.

  • White spaces are also not allowed.

  • Keywords cannot be used as variable name.

Some of the valid variable examples are below

  1. Game_level

  2. _highscore

  3. This_variable_name_is_very_long

Some of the invalid variable examples are below

  1. #run

  2. 2num

  3. int

There are three kinds of variables in Java

  1. Local variables

  2. Instance variables

  3. Class/static variables

Local variables

  • Similar to how an object stores its state in fields, a method will often store its temporary state in local variables. The syntax for declaring a local variable is similar to declaring a field (for example, int count = 0;).

  • There is no special keyword designating a variable as local; that determination comes entirely from the location in which the variable is declared which is between the opening and closing braces of a method. As such, local variables are only visible to the methods in which they are declared; they are not accessible from the rest of the class.

Instance variables

  • Objects store their individual states in "non-static fields", that is, fields declared without the static keyword.

  • Non-static fields are also known as instance variables because their values are unique to each instance of a class

Class/static variables

  • These variables are declared at the top level. They begin their life when first class loaded into memory and ends when class is unloaded. As they remain in memory till classes exist, so these variables often called Class variables. There only one copy of these variables exist

  • These variables are having highest scope that is they can be accessed from any method/ block in a class

  • When no explicit assignment made while declaration they are initialized to default values , depending on their type.

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