Variable in Java

What is a Variable?

• A variable is a named memory location used to store a value.

• That value can be changed during the program execution.

Syntax:

dataType variableName = value;

Ex:

int age=10;
String animal="Tiger";

Here , age and animal are variables that contains some value.

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Types of Variables:

There are mainly three types of variables:

            - Local variable
            - Instance variable
            - Static variable

Local Variable:

• Variable which is declared inside a method , constructor or block is called Local Variable.
• You must initialize the value for local variable, before accessing it.
• These local variables can be accessed within that block only.
• Local Variables don't have Default values.

ex:

class Animal
{

public void Dog()
{
int age=5;   //Local Variable
String name="Puppy";  //Local Variable
System.out.println("Name of the Dog:"+name+"\nAge of the dog:"+age);
}

public static void main (String[] args)
{

   Animal a=new Animal();
   a.Dog();
}

}

Output:

Name of the Dog:Puppy
Age of the dog:5

Here, name and age are the local variables. We can't access the local variables outside the block. If we try to access the local variables outside the block the compiler throws a compilation error.

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Instance Variable:

• Variable which is declared inside a class outside methods, constructor or block is called Instance Variable.
• Instance variables belongs to object.
• Each object has it own copy.
• Instance variables have default value if they are not explicitly initialized.
• We can access the instance variables using objects.

Ex:

class Animal
{
  String name="Tiger";  //Instance Variable
  int age=13;  //Instance Variable 

public static void main (String[] args)
{

   Animal a=new Animal();
   System.out.println("Animal Name:"+a.name);
   System.out.println("Animal Age:"+a.age);

}

}

Output:

Animal Name:Tiger
Animal Age:13

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Static Variable:

• A variable declared inside a class using the static keyword is called a static variable.
• Static variables belongs to class.
• Only one copy of a static variable is created and shared among all objects of that class.

• Static variables have default value if they are not explicitly initialized.

• We can access the static variable using its class name.

Ex:

class Birds
{
static String name="Parrot";  //static variable
static String home="Trees";   // static variable

public static void printing()
{
System.out.println("Bird name:"+name+"\nBird's Home:"+home);
}

public static void main (String[] args)
{
   System.out.println(Birds.name);
   System.out.println(Birds.home);
   Birds.printing();
}
}

Output:

Parrot
Trees
Bird name:Parrot
Bird's Home:Trees

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