Static members are class level members. The
class members which are defined with static keyword is called static
members. There is only one copy of static member for a class, so static
members do not depend on objects. Static members are mainly used for memory
management.
Java Static Members
(1) Static Variable
(2) Static Method
(3) Static Block
(4) Static Nested Class
Static Variable
The member variables which are defined
with static keyword are called static variables. Static member
variables are defined inside a class and outside all instance member methods,
constructors, or any block. A static variable cannot be local variable, if we
do so, we will get compile time error "illegal start of
expression".
Static variables get space in memory
when class loading into JVM and is available till the class removed from JVM.
Static variables can be accessed with
class name
Syntax:
<class-name>.<variable-name>;
Example of static variable in java
public class StaticVariable
{
static
String course = "JAVA";
private
int roll_no;
private
String name;
StaticVariable(String
n, int r)
{
name
= n;
roll_no
= r;
}
public
void showDetails()
{
System.out.println("Name
: "+name+"\nRoll no. : "+roll_no+"\nCourse :
"+course);
}
public
static void main(String[] args)
{
StaticVariable
s = new StaticVariable("John", 32);
s.showDetails();
}
}
OUTPUT:
Name : John
Roll no. : 32
Course : JAVA
Static variables can be of any access
modifier.
Static Method
A static method always defined
with static keyword. A static method belongs to class, not to
objects. There is only one copy of static method for a class.
Static methods cannot access instance
member variables, they can only access static variables.
Static methods get space in memory when
class loading into JVM and is available till the class removed from JVM.
Static methods can be accessed with
class name.
Example of static variable in java
public class StaticVariable
{
static
String course = "JAVA";
private
int roll_no;
private
String name;
StaticVariable(String
n, int r)
{
name
= n;
roll_no
= r;
}
public
void showDetails()
{
System.out.println("Name
: "+name+"\nRoll no. : "+roll_no+"\nCourse :
"+course+"\n");
}
static
void changeCourse()
{
course
= "C#";
}
public
static void main(String[] args)
{
StaticVariable
s1 = new StaticVariable("John", 32);
s1.showDetails();
StaticVariable.changeCourse();
StaticVariable
s2 = new StaticVariable("Andrew", 10);
s2.showDetails();
}
}
OUTPUT:
Name : John
Roll no. : 32
Course : JAVA
Name : Andrew
Roll no. : 10
Course : C#
Static Block
Static block is defined with static keyword.
Static block is used to initialize static members. Static block executes before
main() function, when class is loading into JVM.
Example of static variable in java
public class StaticVariable
{
static
String course;
private
int roll_no;
private
String name;
StaticVariable(String
n, int r)
{
name
= n;
roll_no
= r;
}
public
void showDetails()
{
System.out.println("Name
: "+name+"\nRoll no. : "+roll_no+"\nCourse :
"+course+"\n");
}
static
void changeCourse()
{
course
= "C#";
}
public
static void main(String[] args)
{
StaticVariable
s1 = new StaticVariable("John", 32);
s1.showDetails();
StaticVariable.changeCourse();
StaticVariable
s2 = new StaticVariable("Andrew", 10);
s2.showDetails();
}
static
{
course
= "JAVA";
}
}
OUTPUT:
Name : John
Roll no. : 32
Course : JAVA
Name : Andrew
Roll no. : 10
Course : C#
Static Nested Class
A nested class can be defined
with static keyword.
Example of static nested class in java
public class StaticVariable
{
static
class mainClass
{
static
String course = "JAVA";
private int roll_no;
private String name;
mainClass(String n, int r)
{
name = n;
roll_no = r;
}
public void showDetails()
{
System.out.println("Name : "+name+"\nRoll no. :
"+roll_no+"\nCourse : "+course+"\n");
}
static void changeCourse()
{
course = "C#";
}
}
public
static void main(String[] args)
{
StaticVariable.mainClass s1 = new StaticVariable.mainClass("John", 32);
s1.showDetails();
StaticVariable.mainClass.changeCourse();
StaticVariable.mainClass
s2 = new StaticVariable.mainClass("Andrew", 10);
s2.showDetails();
}
}
OUTPUT:
Name : John
Roll no. : 32
Course : JAVA
Name : Andrew
Roll no. : 10
Course : C#
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