Java Variables

 Variables are containers for storing data values.

In Java, there are different types of variable.


  • String - stores text. String values are surrounded by double quotes

  • int - stores integers (whole numbers), without decimals

  • float - stores floating point numbers, with decimals, such as 9.99 or -1.99

  • char - stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes

  • boolean - stores values with two states(true or false)

     

    Variable Declaration 

    Syntax -:

    type  name_of_variable = value;

    type -:  String/ int/ float/ char/ boolean

    name_of_variable -: such as x,x1,y

    equal sign used to assign values to the variable.

 

        ex -: String name= "mala"

                int age=24;

                float decnum=5.99f; 

                char letter ='D';

                bloolean myBool= true;

 

Final Variables 

    We declare the variable as "final" or "constant", which means unchangeable and read-only.

you can add the "final" keyword if you don't want  to overwrite existing values  


        ex -:  final int num=15;

                num =25   // will generate an error: can't assign a value to a final variable

 

 

The general rules for constructing names for variables (unique identifiers) are _:

  • Names can contain letters, digits, underscores, and dollar signs
  • Names must begin with a letter
  • Names should start with a lowercase letter and it cannot contain white space
  • Names can also begin with $ and _ (but we will not use it in this tutorial)
  • Names are case sensitive ("myVar" and "myvar" are different variables)
  • Reserved words (like Java keywords, such as int or boolean) cannot be used as names

         

 



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