Variable is nothing it is just the name of memory location.
While declaring variables we must follow rules given below.
While declaring variables we must follow rules given below.
Rules for Declaring Variables in Java
1. Variable name must bound with data type. It means while
declaring a variable we must specify its data type.
declaring a variable we must specify its data type.
Ex: int x=10;
2. Reserve word or keywords cannot be taken as a variable
name.
name.
3. C
supports 32 character long variable names while in Java the length of variable
name can be infinite.
supports 32 character long variable names while in Java the length of variable
name can be infinite.
4. Nothing except 0-9, A-Z, a-z, _, $ can be used in variable
name.
name.
5. Variable name must not start with numeric and special
characters are also not allowed.
characters are also not allowed.
Example:
intabc=7; (valid)
int _abc=8; (valid)
int abc8=9; (valid)
int 8abc=10 (invalid)
int $_abc=12; (valid)
int $_abc*=15; (invalid)
6. Variable name should be meaningful.
Example:
string i=”Raj”;
//valid but not meaningful
//valid but not meaningful
string name=”Raj”; //valid and meaningful
Note: Local variables must be initialized before first use.
class demo
{
public
static void main(String…s)
static void main(String…s)
{
int
x; //must be initialized
x; //must be initialized
System.out.println(x);
}
}
Java Variable Types
There are three types of variables in Java that are
instance, local and static.
instance, local and static.
1. Instance Variables
Instance variables are declared in a class, but outside any
method, constructor or block.
method, constructor or block.
2. Local Variables
Local variables are declared in methods, constructors or
blocks. It must be initialized before first use.
blocks. It must be initialized before first use.
3. Static Variables
Static variables are declared with the static keyword in a class, but outside any method, constructor or block.
class A
{
int
x=12; //instance variable
x=12; //instance variable
staticint
y=13; //static variable
y=13; //static variable
public
static void main(String…s)
static void main(String…s)
{
int
z=30; //local variable
z=30; //local variable
System.out.println(x);
System.out.println(y);
System.out.println(z);
}
}