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Types of Variables

Types of Variables:-There are total three types of variables in java, according to the place where variables declared. Variables may be primitive types or secondary type.

 1)   Instance variable or non static instance variable.
 2)   Static variable.
  3)  Local variable.

Instance variable: - A variable which is declared inside class but outside methods, called instance variable. Instance variables are directly related to objects, each object of class contains separate copy of instance variables of class. All instance variables occupied memory inside object and initialize with default value when object created. Object always created in heap area of jvm at run time not at compile time.
Example:-

class Student
{
String name;
String lastName;
int rollNo;
String course;
float percentage;
}

In the above class all variables are instance variable.

Static variable:-A variable which is declared inside class but outside method with static modifier, called static variable. Static variables are class level variables. Static variable occupied memory once in life at the time of class loading from hard disk to RAM. Static variable occupied memory in class area of jvm.

  Example:-

class Student
{
static String collegeName;
String name;
String lastName;
int rollNo;
String course;
float percentage;
}
In the above program onetime memory allocated to collegeName, and for remaining variables allocates memory each time when object created.each object can use static variables.

Local variable:-A variable which is declared inside class and inside function called local variable. Local variables occupied memory inside stack memory of jvm when control goes to the variables. Local variable must be initialized before use.

Example:-

class Student
{
String name;
Int rollNo;
void get(String s,int p)
{
name=s;
rollNo=p;
}
}
In the above program s and p are local variables declared in get function, when get function call then memory will allocate to s and p inside stack memory of jvm.




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