Static
Block in Java:-
The
purpose of static block is to initialize static data member’s only
once static block and execute only once when the class is loaded into
the main memory before executing the main method.
Syntax:-
Static
{
Block of statements (s);
……….initialize of static data members.
}
When
we write a static block and main method in a single Java
program then JVM executes static block first and later main method
only once.
Writing
block is optional when we write static block & constructors in a
Java
program then JVM will executes static block only once &
constructors will execute each and every time.
In
static block we can access / initialize only static data members but
not instance data members where as both instance & static data
members can be access in constructor.
In
one Java
class we can write any number of static blocks but all these types of
static blocks will be treated as single static block and gives the
output in that order in which we write.
Whenever
we initialize a static data member in the class then by default that
class will contain then system defined static block.
**
write a Java
program which will illustrate the concept of static block.
class
SBEX1
{
static
{
System.out.println("I
am From Static Block");
}
public
static void main(String[] args)
{
System.out.println("I
am from main()");
}
}
Instance
Block:-
The
purpose of instance block is exactly similar to default constructor
of the particular class.
Instance
block will execute each and every time whenever an object is created
before executing the constructor and after executing the static
block.
Static
block will execute only once when the class is loaded in the main
memory for initializing the data in main memory whereas instance
block will be calling each and every time whenever an object is
created before the constructor and it is used for initializing
instance data members of a class.
Syntax:-
{
Block of statements (s);
……….initialize of instance data members.
}
We
can write any number of instance blocks but all of the instance block
will be treated as single instance block and they will be executed in
which order they write.
**
write a Java
program which will illustrate the concept of instance block.
class
IBEX1
{
static
{
System.out.println("SB...........IBEX1");
}
{
System.out.println("IB............IBEX1");
}
IBEX1()
{
System.out.println("IBEX1..........DC");
}
}
public
static void main(String[] args)
{
System.out.println("I
am from main()");
IBEX1
t1=new IBEX1();
IBEX1
t2=new IBEX1();
}
}
