Skip to main content

Example of Variables

Example1:-

class Student
{
String name;
int roll;
String address;
String course;
String instName;

void getData()
{
System.out.println("Student information is:-");
System.out.println("Name: "+name);
System.out.println("RollNumber: "+roll);
System.out.println("Address is: "+address);
System.out.println("Course is : "+course);
System.out.println("Institute is : "+instName);
}
public static void main(String[]args)
{
Student s=new Student();
s.getData();
}
}

Output:-

C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student

Student information is:-
Name: null
RollNumber: 0
Address is: null
Course is : null
Institute is : null

In the output 0 is default value of integer variable and null is default value of all secondary data types.
In the above program we have two types of variables, instance variable and local variable. Total five instance variables are declared in class Student (name, roll, address, course and instName) and one local variable declared in main method(s).
In the above code s is local variable because s is declared inside main method, s will get memory inside stack when control goes to the line Student s=new Student (); in this line s is reference variable of class Student and right hand side part of line that is new Student ();, create a object and assign the address of created object to left hand side variable s.
In new Student (), new is a keyword, is used for creating run time object and Student is a class so when the new Student() line executed then  inside heap area a object is created and all non static instance variables takes memory inside object and initialize with default value. so for each object all non static variable occupied memory in object.

Example2:-

class Student
{
String name;
int roll;
String address;
String course;
String instName;

void setData()
{
name="Rudraksha";
roll=101;
address="106,Shiv city Indore";
course="B.Tech";
instName="IIT Indore";
}
void getData()
{
System.out.println("Student information is:-");
System.out.println("Name: "+name);
System.out.println("RollNumber: "+roll);
System.out.println("Address is: "+address);
System.out.println("Course is : "+course);
System.out.println("Institute is : "+instName);
}
public static void main(String[]args)
{
Student s=new Student();
s.getData();  //print default value for all instance variable.
s.setData();
s.getData();  //print set values of setData function.
}
}

Output:-

C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student

Student information is:-
Name: null
RollNumber: 0
Address is: null
Course is : null
Institute is : null
Student information is:-
Name: Rudraksha
RollNumber: 101
Address is: 106,Shiv city Indore
Course is : B.Tech
Institute is : IIT Indore

In the above program instName variable has same value IIT Indore for every object, so no need to allocate memory for this variable for each object.
We have to declare instName variable as a static and assign value IIT Indore, this variable takes memory in class area, one time in whole life at the time of class loading and every object share this variable.

Example3:-

class Student
{
String name;
int roll;
String address;
String course;
static String instName="IIT Indore";

void setData()
{
name="Rudraksha";
roll=101;
address="106,Shiv city Indore";
course="B.Tech";
}
void getData()
{
System.out.println("Student information is:-");
System.out.println("Name: "+name);
System.out.println("RollNumber: "+roll);
System.out.println("Address is: "+address);
System.out.println("Course is : "+course);
System.out.println("Institute is : "+instName);
}
public static void main(String[]args)
{
Student s=new Student();
s.getData();
s.setData();
s.getData();
}
}

Output:-

C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student

Student information is:-
Name: null
RollNumber: 0
Address is: null
Course is : null
Institute is : IIT Indore
Student information is:-
Name: Rudraksha
RollNumber: 101
Address is: 106,Shiv city Indore
Course is : B.Tech
Institute is : IIT Indore

Example4:-

class Student
{
String name;
int roll;
String address;
String course;
static String instName="IIT Indore";

void setData()
{
name="Rudraksha";
roll=101;
address="106,Shiv city Indore";
course="B.Tech";
}
void getData()
{
System.out.println("Student information is:-");
System.out.println("Name: "+name);
System.out.println("RollNumber: "+roll);
System.out.println("Address is: "+address);
System.out.println("Course is : "+course);
System.out.println("Institute is : "+instName);
}
public static void main(String[]args)
{
Student s=new Student();
s.setData();
s.getData();
}
}

Output:-
C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student

Student information is:-
Name: Rudraksha
RollNumber: 101
Address is: 106,Shiv city Indore
Course is : B.Tech
Institute is : IIT Indore




Labels:

Comments

Post a Comment

Popular posts from this blog

Inner classes

Inner Classes:- class inside class or interface called inner class or nested class. Advantage of inner classes is grouping multiple classes and interfaces into a single class. Another big advantage of inner class is that inner class can happily access all the data or variables of outer class directly. Types of Nested classes:- There are two types of nested classes static and non-static nested classes. (A)Non –static inner classes:- 1)     Member inner class 2)     Anonymous inner class 3)     Local inner class (B)Static nested class Example1:-Outer.java class Outer { class Inner { void disp() { System.out.println("Hello This is Inner class Method"); } } public static void main(String[]args) { Inner in=new Inner(); in.disp(); } } Output:- C:\JAVATECH>javac Outer.java Outer.java:12: error: non-static variable this cannot be referenced from a static context Inner in=new Inner(); ...
Post a Comment
Read more

Small concept about OOPs

Some small concept about OOPs:- In many books and website write about OOPs concepts as hundred percent object oriented, pure object oriented and partial object oriented language. Hundred percent object oriented:- In the hundred percent object oriented movie hero is object, without object program is incomplete that means can not execute program without object. Without class and object programming or application development is not possible. Example of hundred percent object oriented language is  Smalltalk . Pure object oriented:- In the object oriented cinema obviously object is the hero. In pure object oriented language object having same importance but in this having some relax that is without creating object we can successfully execute our application. So in the object oriented programming without class we cannot create or run our application, class is must. Example of pure object oriented language is  Java . Partial object oriented:- In this type of la...
Post a Comment
Read more

Inheritance-4

Example10:- class Student { Student() { System.out.println("This is super class Zero argument constructor"); } Student(String s) { System.out.println("This is super class One argument constructor"); } } class Test extends Student { Test() { super(null); System.out.println("This is sub class Zero argument constructor"); } public static void main(String[]args) { Test t=new Test(); } } Output:- C:\JAVATECH>javac Test.java C:\JAVATECH>java Test This is super class One argument constructor This is sub class Zero argument constructor Example11:- class Student { Student() { System.out.println("This is super class Zero argument constructor"); } Student(String s) { System.out.println("This is super class One argument constructor"); } } class Test extends Student { Test() { super(); super(null); System.out.println("This is su...
Post a Comment
Read more