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Usage of Static in Java programming language
Usage of Static in Java programming language
In this tutorial, we will discuss Usage of Static in Java programming language
In Java programming language, Static keyword(reserve word) is used to memory management mainly. But “static” use a lot of ways in Java. Static can be applied in Java’s:
- fields(variable) ,
- methods
- inner class and nested class
- blocks.
static variable
We can declare any variable as static(with the static keyword) that is called the static variable.
The static variables can be used to refer to the common property of all object in class such as blocks, methods and class.
Declaration
The syntax of static variable
static <data_type><variable_name>
Example
static int age; static string name;
we can use the static keyword in the class level variable(instance variable).
class student{
int age;
int marks;
//normal variable inside the class
static string school_Name;
//static variable inside the class
}
Usage of the static variable in Java
Usage 1- Static variables are shared among all the instances of the class
Example
class Family_members{
int age; //instance variable declaration
String f_Name;
//non static variable inside the class
static String l_Name="Kanapathy";
//static variable inside the class
Family_members(int age_1,String name_1){
age=age_1;
f_Name=name_1;
}
void display()
{
System.out.println(f_Name+" "+l_Name+" "+"age is"+" "+age);
}
public static void main(String args[]){
Family_members f1=new Family_members(24,"Kamalan");
Family_members f2=new Family_members(17,"Ramesh");
Family_members f3=new Family_members(20,"Nimalan");
f1.display();
f2.display();
f3.display();
}
}
When the above code is executed, it produces the following results:
Kamalan Kanapaty age is 24 Ramesh Kanapaty age is 17 Nimalan Kanapaty age is 20
In this example, the static variable (static String l_Name=”Kanapathy”;) string 1_Name is shared to all the instance of the class
Usage 2- Static variables can access directly in static methods
The static variable can be accessed without using an object of its class are created. So we can access directly
class ExampleStatic{
static int age;//static veriable
static String name;
static void display(){//static method
System.out.println("age is :"+age);
System.out.println("name is :"+name);
}
public static void main(String args[]){
display();//can be access derectly
}
}
When the above code is executed, it produces the following results:
age is :0 name is :null
In the above program, we are accessing static method display() without creating any object in this class
Non Static variables cannot access directly in static methods
class ExampleNonStatic{
int age; //non static variable
String name;
static void display(){
System.out.println("age is "+age);
System.out.println("name is "+name);
}
public static void main(String args[]){
display();
}
}
When the above code is executed, it produces the following results:
Compile time error
The non-static variable can not be accessed without using any object of its class
Usage 3- Static variables can access directly in the main method in Java
class ExampleStatic1{
static int age=34; //non static variable
static String name="suman";
public static void main(String args[]){
System.out.println("age is "+age);
System.out.println("name is "+name);
}
}
When the above code is executed, it produces the following results:
age is 34 name is suman
Non-static variables cannot be accessed directly in the main method in Java
program 2
class ExampleStatic1{
int age=34; //non static variable
String name="suman";
public static void main(String args[]){
System.out.println("age is "+age);
System.out.println("name is "+name);
}
}
When the above code is executed, it produces the following results:
Compile time error
In the above program, age and name are non-static variables. it cannot be accessed from the main method
static method
When we apply static keyword with any method, it is called a static method. Any static member can be accessed before any object of its class is created. and without reference any object
Declaration
The syntax of the static method
static <return_type><method_name>
Example
static void display() {}
static string student_name() {}
Program 1
class Static_Method{
//this is main method inside the class
public static void main(String args[]){
// here we can call the static method
my_School();
}
//this is static method();
static void my_School()
{
System.out.println("this is my school");
}
}
When the above code is executed, it produces the following results:
this is my school
The static method (my_School())can be accessed before any object of its class is created. and without reference any object.
So we can directly access this static method(my_School())
Program 2
The main method is static, the static variable can be accessed directly from the main method
class Static_methodEx{
static int marks=56;//static veriable
static String subject="Science";
public static void main(String args[]){
//main method as static
System.out.println("Marks is :"+marks);
System.out.println("Subject is :"+subject);
}
}
When the above code is executed, it produces the following results:
Marks is :56 Subject is :Science
Program 3
If the main method is static, static methods and non-static methods can be accessed directly from the main method
class Static_methodEx2{
static int marks=78;//static veriable
static String subject="Mathematics";
static void getDet(){//static method
System.out.println("Marks is :"+marks);
System.out.println("Subject is :"+subject);
}
void display(){//non static method
getDet();//static method called inside non static method
}
public static void main(String args[]){
//main method is also static method
Static_methodEx2 obj=new Static_methodEx2();
//object create to call non static method
obj.getDet();
}
}
When the above code is executed, it produces the following results:
Marks is :78 Subject is :Mathematics
static block
Declaration
The syntax of the static block
static {}
Example
static {
//some code here
}
program 1
class My_Details{
static int my_Age; //static variable
static String my_Name;
static double my_Weight;
static{ //static block
my_Age=23; //initialized static variable
my_Name="Robbert hook";
my_Weight=75.9;
}
public static void main(String args[]){
System.out.println("My age is :"+my_Age);
System.out.println("My name is :"+my_Name);
System.out.println("My age is :"+my_Weight);
}
}
When the above code is executed, it produces the following results:
My age is :23 My name is :Robbert Hook My weight is :75.9
Multiple static blocks
A class can have more than one static block which is known as multiple static blocks. Now let’s see how to work multiple static blocks in Java
Declaration
The syntax of the static block
static {}
static {}
Example
static {//first static block
//some code here
}
static { // second static block
//some code here
}
class My_Details{
static int age; //static variable
static String name;
static double weight;
static{ //first static block
age=23; //initialized static variable
name="Robbert hook";
weight=75.9;
}
static{ //second static block
age=21; //initialized static variable
name="Jhon seela";
weight=100.9;
}
public static void main(String args[]){
System.out.println("Age is :"+age);
System.out.println("Name is :"+name);
System.out.println("Weight is :"+weight);
}
}
When the above code is executed, it produces the following results:
Age is :21 Name is :Jon seela Weight is:100.9
Static blocks are executed according to the given order. therefore first static block is overwritten by second static block
There are other Java language keywords that are similar to this keyword
float keyword in Java
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