Java Variables and Types of variables in Java

 

Variable: 

The name of memory allocation which is used to store the data type during time execution.it is a combination of two words “vary or able” which means its value can be changed. 

Deceleration: 

We declare the variable as: Data_type Varible_Name; 

Initialization: 

We initialize the variable as: Varible_Name=value; 

Definition: 

We define the variable like as: Data_type Varible_Name = Value; Example: 

Int y; (Declaration of variable) 

y=10; (Initialization of variable) 

Int x=10; (Definition of variable) 

Types of Variables 

There are three types of variable are as follows: 

1. Local variable: 

 A type of variable that is used inside the function and never accessed outside. 

2. Instance variable: 

 A type of variable that is declared inside the class and outside the function. It accesses the value through the object. 

3. Static variable: 

 A type of variable that is

declared with a static keyword throughout the program. 

Example to understand the types of variables in java 

Program:

class Variable { 

 static int x=23; //static variable 

 float instance=99; //instance variable 

 void local(){ //local variable 

 double a=34; 

 float b=45.5f; 

 double ab=a+b; 

 System.out.println("Sum of ab is: "+ab); System.out.println("The value of X: "+x); 

} 

 public static void main(String[] args) { 

Variable obj=new Variable(); 

obj.local(); 

 System.out.println("Instance value: "+obj.instance);  } 

 } 

Output: 

 Sum of ab is: 79.5 

 The value of X: 23 

 Instance value: 99.0 

 ★ How do we create the object in java? 

We create the object as:

Class_name object_Name = new Class_function();

Here we discuss some examples of variables in java. 

★Add Two Numbers 

class Add { 

 public static void main(String[] args) { 

 float a=12.5f; 

 double b=44.6d; 

System.out.println("The sum of two numbers is: "+a+b); 

} 

} 

Output: 

 The sum of two numbers is: 12.544.6

★Widening: 

 Widening is also known as upcasting. It is the conversion of greater primitive type value into smaller primitive type value. 

Example to understand the widening in java 

Program:

class Widening { 

 public static void main(String[] args) { 

 int x=23; 

 float a=x; 

 long b=x; 

 double c=x; 

 System.out.println("Float: "+a); 

 System.out.println("Long: "+b); 

 System.out.println("Double: "+c); 

} 

} 

Output: 

 Float: 23.0 

 Long: 23 

 Double: 23.0 

★Narrowing(Typecasting): 

Narrowing is also known as downcasting. The conversion of narrowing is small primitive data type value into large primitive data type value. 

Example to understand the narrowing in java 

Program:

class Narrowing { 

 public static void main(String[] args) { 

 double a=23.5; 

float d=55.05f; 

long b=(long)a; 

double c=(double)a; 

int x=(int)a; 

float y=(float)a; 

byte z=(byte)d;

 System.out.println("Long: "+b);  System.out.println("Double: "+c);  System.out.println("Int: "+x); 

 System.out.println("Float: "+y);  System.out.println("Byte: "+z); 

} 

} 

Output: 

 Long: 23 

 Double: 23.5 

 Int: 23 

 Float: 23.5 

 Byte: 55 

★ Overflow 

Program:

class Overflow { 

 public static void main(String[ ] args) { double db=150d; 

byte byt=(byte)db; 

System.out.println("byte"+byt); 

} 

} 

Output: 

 byte-106 

★ Underflow

Program:

class Underflow { 

 public static void main(String[ ] args) { double db=-200d; 

byte byt=(byte)db; 

System.out.println("Byte "+byt); 

} 

} 

Output: 

 Byte 56