Variables in JAVA programming Hands on coding

1. What is Variable ?

• Variable is the name of storage space which can be used to store data.
• The value of the variable may change. It contains last value which is stored into it.
• Variable should be always declared with data type.

2. Variable Declaration

 int num;   
 float height;   
 char name;   

• Here num is a variable of  int type.
• height is a variable of float type.
• name is a variable of type char.

3. Variable Initialization

You can initialize the variable at the time of declaration of variable only or you can initialize after the  declaration.

 int registration_num=201;   
 float height=5.6;   
 char division='A';   

• 201 is the value of registration_num. 
• 5.6 is the value of height. 
• A is the division. 

Note; Character value is always written in single quotes.

Let's see another method of variable Initialization

You can initialize the variable after the declaration of variable.

int register_num; 

float height; 

char division; 

registration_num=201; 

height=85.6; 

division='A'; 

Rules to create the variable;

• First letter of any variable must be either alphabet or underscore(_).
• The variable name must not begin with digits.
• Next to the first character it may contain combination of alphabets or digits.
• White spaces are not allowed.
• Variable name must not be a keyword.

Types of Variable

1. Local Variable
2. Instance Variable
3. Static Variable

1. Local Variable

• The variable declared within the body of the method or constructor or block can be called as local variable.
• You can use local variable only inside that function in which it will be declared and it can be a static variable.

 class Example   
 {   
  public void add()   
   {   
    int x,y=15,z=25;  //declaring local variable   
    x=y+z;   
    System.out.println("Add="+x);   
   }   
   public static void main(String[] args)   
   {  
     Example obj=new Example();   
     obj.add();   
   }   
 }   

/ ### Output ### 

Add=40 / 

Instance Variable

• This variable can be declared inside the class but outside the body of the constructor/block is called instance variable.
• You can use instance variable 
• anywhere in the program.

 class Easy   
 {   
   //these instance variabe can be used   
  //inside all the function of this class   
   int x,y=30,z=20;   
   public void add()   
   {   
     x=y+z; //accessing instance variable   
    System.out.println("Add="+x);   
   }   
   public void sub()   
   {  
    x=y-z;   //accessing instance variable   
   System.out.println("Sub="+x);   
   }   
   public static void main(String[] args)   
   {   
    Easy obj=new Easy();   
    obj.add();   
    obj.sub();   
   }   
 }   

/ ### Output ### Add=30 Sub=10 / 

Static Variable

• This is the variable which will be declared with static keyword, inside a class but outside the body of the method or constructor or block.
• Static variable will be stored in the static memory.
• Static variables will be created when the program starts and it will be destroyed when the program stops.
• You can call static variable by the name of class directly.

 class Easy   
 {  
   //declaring static variable   
   static String text="You are a smart guy.";   
   public static void main(String[] args)   
   {   
      System.out.println(Easy.text);   
   }   
 }   

/ ### Output ### 

You are a smart guy. /

This is regarding variables in JAVA. 

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