Variable
Variable is name of reserved area allocated in memory. In other words , it name of memory location. It is a combination of "very+able" that means its value can be changed.
Example:
int data=10;
here data is variable.
There are three types of variables in java:
- Local Variable
A variable which is declare inside the method is called local variable.
- Instance Variable
A variable which is declared inside the class but outside the method, is called instance variable. It is not declared as static.
- Static Variable
A Variable that is declared as static is called static variable. It cannot be local.
Example for better understanding variables
Class A{
int data=50;//instance variable
static int m=20;//static variable
void method(){
int n=90;//local variable
}
}//end of class
Data Type in Java
Datatype represents the different values to be stored in the variable. In java, there are two types of datatypes:
- Primitive data type
- Non-primitive data type
Data type Default Value Default Size
Boolean false 1 bit
Char '\u000' 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 \u000 is the lowest range of Unicode system.
Java variable example: Add Two Numbers
class add {
public static void main(String [] args){
int a=10;
int b=10;
int c=a+b;
System.out.println(c);
}
}
Output: 20
Java variable example : Narrowing (Typecasting)
class Type{
public static void main(String [] args){
float f=10.5f;
//int a=f;//compile time error
int a=(int)f;
System.out.println(f);
System.out.println(a);
}
}
Output:
10.5
10
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