|
|
|
A variable can be thought of as a container which holds value for you during the life of your program.
Every variable is assigned a data type which designates the type and quantity of a value it can hold.
|
The different Data Type are ---
Integer data types
byte (1 byte)
short (2 bytes)
int (4 bytes)
long (8 bytes)
Floating Data type
float (4 bytes)
double (8 bytes)
Textual Data Type
char (2 bytes)
Logical
boolean (1 byte) (true/false)
Points to Remember:
- All numeric data types are signed(+/-).
- The size of data types remain the same on all platforms (standardized)
- char data type in Java is 2 bytes because it uses UNICODE character set. By virtue of it, Java supports internationalization. UNICODE is a character set which covers all known scripts and language in the world
To use a variable in your program you need to perform 2 steps
- Variable Declaration
- Variable Initialization
1) Variable Declaration
To declare a variable , you must specify the data type & give the variable a unique name.
Examples of other Valid Declarations are
int a,b,c;
float pi;
double d;
char a;
2) Variable Initialization:
To initialize a variable you must assign it a valid value.
Example of other Valid Initializations are
pi =3.14f;
do =20.22d;
a=’v’;
You can combine variable declaration and initialization.
Example :
int a=2,b=4,c=6;
float pi=3.14f;
double do=20.22d;
char a=’v’;
Variable Type Conversion & Type Casting
A variable of one type can receive the value of another type.Here there are 2 cases -
case 1) Variable of smaller capacity is be assigned to another variable of bigger capacity.
This process is Automatic, and non-explicit is known as Conversion
case 2) Variable of larger capacity is be assigned to another variable of smaller capacity
In such cases you have to explicitly specify the type cast operator. This process is know as Type Casting.
In case, you do not specify a type cast operator, the compiler gives an error. Since this rule is enforced by the compiler , it makes the programmer aware that the conversion he is about to do may cause some loss in data and prevents accidental losses.
Assignement: To Understand Type Casting
Step 1) Copy the following code into an editor.
class Demo{
public static void main(String args[]){
byte x;
int a=270;
double b =128.128;
System.out.println("int converted to byte");
x=(byte) a;
System.out.println("a and x "+ a +" "+x);
System.out.println("double converted to int");
a=(int) b;
System.out.println("b and a "+ b +" "+a);
System.out.println("\n double converted to byte");
x= b;
System.out.println("b and x "+b +" "+x);
}
}
Step 2) Save, Compile & Run the code.
Step 2) Error =? Try to debug. Hint - Typecasting is missing for one operation.
Back to Java Tutorials Index Page
|