Variable and Data Type

Education is not limited to just classrooms. It can be gained anytime, anywhere... - Ravi Ranjan (M.Tech-NIT)

Variables and Data Types in Java

Variable is a name of memory location. There are three types of variables in java: local, instance and static.

There are two types of data types in java: primitive and non-primitive.

Variable

Variable is name of reserved area allocated in memory. In other words, it is a name of memory location. It is a combination of "vary + able" that means its value can be

changed.

variables in java

  1. int data=50;//Here data is variable  

Types of Variable

There are three types of variables in java:

  • local variable
  • instance variable
  • static variable
  • types of variables in java

 

1) Local Variable

A variable which is declared inside the method is called local variable.

2) Instance Variable

A variable which is declared inside the class but outside the method, is called instance variable . It is not declared as static.

3) Static variable

A variable that is declared as static is called static variable. It cannot be local.

We will have detailed learning of these variables in next chapters.

Example to understand the types of variables in java

  • class A{  
  • int data=50;//instance variable  
  • static int m=100;//static variable  
  • void method(){  
  • int n=90;//local variable  
  • }  
  • }//end of class 

Data Types in Java

Data types represent the different values to be stored in the variable. In java, there are two types of data types:

  • Primitive data types
  • Non-primitive data types
  • datatype in java

 

Data Type

Default Value

Default size

Boolean

false

1 bit

char

'u0000'

2 byte

byte

0

1 byte

short

0

2 byte

int

0

4 byte

long

0L

8 byte

float

0.0f

4 byte

double

0.0d

8 byte

 

Why char uses 2 byte in java and what is u0000?

It is because java uses Unicode system than ASCII code system. The u0000 is the lowest range of Unicode system. To get detail explanation about Unicode visit next page.

Java Variable Example: Add Two Numbers

  1. class Simple{  
  2. public static void main(String[] args){  
  3. int a=10;  
  4. int b=10;  
  5. int c=a+b;  
  6. System.out.println(c);  
  7. }}  
  8. Output:

    20
    

Java Variable Example: Widening

 

  1. class Simple{  
  2. public static void main(String[] args){  
  3. int a=10;  
  4. float f=a;  
  5. System.out.println(a);  
  6. System.out.println(f);  
  7. }}  

Output:

10
10.0

Java Variable Example: Narrowing (Typecasting)

 

  1. class Simple{  
  2. public static void main(String[] args){  
  3. float f=10.5f;  
  4. //int a=f;//Compile time error  
  5. int a=(int)f;  
  6. System.out.println(f);  
  7. System.out.println(a);  
  8. }}  

Output:

10.5
10

Java Variable Example: Overflow

 

  1. class Simple{  
  2. public static void main(String[] args){  
  3. //Overflow  
  4. int a=130;  
  5. byte b=(byte)a;  
  6. System.out.println(a);  
  7. System.out.println(b);  
  8. }}  

Output:

130
-126

Java Variable Example: Adding Lower Type

 

  1. class Simple{  
  2. public static void main(String[] args){  
  3. byte a=10;  
  4. byte b=10;  
  5. //byte c=a+b;//Compile Time Error: because a+b=20 will be int  
  6. byte c=(byte)(a+b);  
  7. System.out.println(c);  
  8. }}  

Output:

20