Types of variables

Into the our language java based on this their is the two types of variables that we have. types of variable that based on the values represented by the variable and based on the type of position that based on the variable .

A. Based on the value

1. Primitive

2. Reference

B. Based on the position

1. Instance

2. Static

3. Local

EXPLAIN::

A::

Based on the value are again subdivided into the two types that are, Primitive and reference into this value of the variable that declares the way fir the primitive and reference

i. Primitive

primitive are the variables that declares the value directly or declares the value into the datatypes that variables we called as the primitive variables

EX: int x=10;

int is the container that stores the value of the variable is int x=10

ii. Reference

reference is the variables that is obj . obj is the variables into the reference that creates when we create into the class of main method. this objects are different for the same class that means this is the property of the class that means we can say that obj are the variables of the class. in short we say reference for them.

EX: Employee obj=new Employee();

here obj is the reference variable. and Employee() is the constructor for the initialization of the obj as empty. Employee is to show the class name .

B::

Based on the position of the declaration and behavior that means it is not depends upon any container. Is only depends upon the where we declare the variable this shows the exact variable name. if we declare into the main method body or any thing else, this all variables are subdivided into the another 3 types of variables.

i. Instance

if the value of the variables is changing object to object is called instance variables

EX: class Employee{

string name;

int id;

}
NOTE:: Instance variable should be declared into directly class without into any constructor, function and static block.

function:

void Employee(){

int x=10;

}
Static:

static{
int x=10;

}
constructor:

Employee(){
int x=10;

}

this all the value declaring into the different different positions like function, constructor and static block are not be considered and as the instance variables.

only the declaration directly into the class is considered as the instance variables.

Instance variables are created when the object is created and destroyed when the object is destroyed.

Instance variables are created into the heap memory and instance variables is created into the objects.

Q1. class Employee(){

string name;

int id;

p.v.s.m(){
s.o.p.ln(name);

}}

output::

ERROR:: Non-static context cannot be access from the static context

Instead this do this above code

into the p.v.m.s

p.v.m.s(){
Emp obj=new Employee();

s.o.p.ln(obj.name);

}

NOW the output is

NULL → default value

Q2,.NOW again question;

class X{
int y=10;

p.s.v.m(){
X x=new X();

x.m1();

}

void m1(){
s.o.p.ln(y);

}}

OUTPUT::
10

into the object x the instance variable is into the instance block of object. Also, the m1 is the method into the instance block that’s why this m1 can be accessible for y=10. but, if the m1 method is into the static block then it can’t be accessible into the instance block.

Q3..

class X{

p.s.v.m.(){
int x;

S.o.p.ln(x);

}}

OUTPUT::
ERROR:: Local variable must be initialize

Explain::

For this we consider the bus and passenger example we declared the variable into the main method block same like the passenger and conductor are into the bus but this is the lots of passengers into the bus that’s why the conductor can not click that the the passenge is take ticket from him . same like into the given code if we declare variable into the main method this got erro because their is no any initialization for the local variable.

1. JVM provides default values static to instatic variables

2. JVM won’t provide int y=20; default value to local variable

ii. Static variables

static variables are the variables in which it’s value does not changes from object to object then we use static variables.

we can declare static variable inside the class but outside method, constructor, or block, prefixing with static keywords.

class Employee{

string name;

Static string company_name;

p.s.v.m(){

s.o.p.ln(Company_name);

So.p.ln(Name);

}}

OUTPUT::
Error: Non-staic variable cannot be access from the static context and method. Static variable is stored into the method area not into the stack

If any object is change then the static variable that changes that are reflected to all other objects.

class Employee{

string name=”x”;

Static string company_name=”sielabs”;

p.s.v.m(){

s.o.p.ln(Company_name);

S.o.p.ln(Name);