Data types and Variables

 Datatype:
    Specifies the size and then type of values that can be stored in an identifier.

    They are used to represent how much memory is required to hold the data.

Variables: 

    Variables are nothing but a name given to storage area.

Three types of variables:

    1. Local Variable

    2. Instance variable

    3. Static variable

1. Local Variable: A local variable in Java is a variable that’s declared within the body of a method. Then you can use the variable only within that method. Other methods in the class aren’t even aware that the variable exists. If we are declaring a local variable then we should initialize it within the block before using it.

2. Instance variable:

The variables which are declared inside a class outside any method /block/ a constructor are known as instance variables.

     * For Instance variables JVM will automatically assign them with their default values.

* We can access instance variables in 2 ways, by using identifier name & by using class instance / class object.

* For instance variables memory will be assigned at the time of creating a class instance/object.

*For instance of a class there will be a separate copy of instance variables will be created.

3. Static variable: 

The variables which are declared as class ouside any method or a block or a constructor with static keyword are known as static variables.

* For Static variables JVM will automatically asign them with their default values.

* We can access a static variable in 3 ways- by using identifier name, by using class instance, by using class name.

* There will be only one copy of static variable available throughout the program.

* For final static variable JVM will not provide any default values, it 
is the responsibility of the programmer to initilize that variable, otherwise we will be getting compile time errors.