Java static keyword

A static member (block, variable, function, or nested class) must be created by adding the term static before its definition. When a class member is designated as static, it can be accessed without an object reference and before the class's objects are created.
The main method of a class is generally static.

The static keyword is a non-access modifier and can be used for the following in the Java programming language.

Static keyword can be used as:

• Java static Variable
• Java static Method
• Java static Block
• Java static Classes

Java static variable

A variable is considered static if you declare it to be static keyword before variable.

• When a variable is defined as static, it creates one copy and shared by all objects within the class. Essentially, static variables are global variables. The same static variable is shared to all class objects.
• Only at the class level may static variables be created. When the class is loaded, static variable only receives one memory allocation within the class area.
• Static variables and blocks are executed in the order that they appear in a programme.

 class   Company{ 

  int   Empid; 

  String EmpName;  

  String  Company="DockerTpoint";  

  } 

Assuming my company has 2000 employees, each time an object is created, all instance data members will receive RAM. Since each employee has a distinct EmpName and Empid, using an instance data member is appropriate in this situation. The term "Company" here refers to the attribute that all objects share. If we set it to a static, the memory will only be retrieved once for this particular field.

How to declare static variable

 // Java  program using static variable  

class Emp{  
    int EmpId;
    String EmpName;  
    static String CompanyName ="DockerTpoint";
        Emp(int EmpId, String EmpName ){  
            this.EmpId = EmpId;  
            this.EmpName = EmpName;  
        }   
        void display(){
            System.out.println("Welcome to DockerTpoint");
            System.out.println("Your Empid is "+EmpId+",Your official name is "+EmpName+
                " & Your Company name is "+CompanyName+".\n");
         }  
}  
public class Company{  
    public static void main(String args[]){  
        Emp emp1 = new Emp(40139522,"Meena");  
        Emp emp2 = new Emp(40139524,"Alok");  
        //we can change the Company of all objects by uncomment below line of code  
        //Emp.Company="ProPoint";  
        emp1.display();  
        emp2.display();  
    }  
}
    

Welcome to DockerTpoint 
Your Empid is 40139522,Your Officia name is Meena & Your Company name is DockerTpoint.  

Welcome to DockerTpoint 
 Your Empid is 40139524,Your Officia name is Alok & Your Company name is DockerTpoint. 

Java static Method

A method is said to as static when the static keyword is used in its declaration. The main() function is the most typical illustration of a static method.It is possible to access any static members without objects of its class.
There are various limitations on methods that are marked static:

• A static method, is directly linked to the class itself, unlike other methods associated with objects
• It is possible to call a static method without first creating a class object.
• A static method have the ability to access the values of static data members.
• A static method cannot be make in any way reference to this or super.

Restrictions on static method

• Static methods cannot directly access or call non-static methods or data members.
• Super and this cannot be used together in a static keyword

How to declare static method

 // Java  program using static variable  

class Emp{  
    int EmpId;
    String EmpName;  
    static String CompanyName ="DockerTpoint";
    Emp(int EmpId, String EmpName ){  
        this.EmpId = EmpId;  
        this.EmpName = EmpName;  
    }
    static void CompanyChange(){  
        CompanyName = "ProPoint";  
     }  
    void display(){
     System.out.println("Welcome to "+CompanyName);
     System.out.println("Your Empid is "+EmpId+",Your official name is "+EmpName+
         " & Your Company name is "+CompanyName+".\n");
     }  
}  
public class Company{  
   public static void main(String args[]){
       Emp.CompanyChange();
       Emp emp1 = new Emp(40139522,"Meena");  
       Emp emp2 = new Emp(40139524,"Alok");   
       emp1.display();  
       emp2.display();  
    }  
}

Welcome to ProPoint 
Your Empid is 40139522,Your Officia name is Meena & Your Company name is ProPoint.  

Welcome to ProPoint 
 Your Empid is 40139524,Your Officia name is Alok & Your Company name is ProPoint. 

The Java main function is static, why?

It is due to the fact that calling a static method is not needed of the object. If it were a non-static method, the problem of excessive memory allocation would arise since JVM first constructs an object before calling the main() method.

Java static block

If a calculation is required to initialise static variables, you can create a static block that will run only once, at class initialization.

• Static block in java is used to initialize the static data member.
• During classloading, a Java static block is executed before the main method.

How to declare Java static block

 // Java  program using static variable  

class Emp{  
    int EmpId;
    String EmpName;  
    static String CompanyName ="DockerTpoint";
    Emp(int EmpId, String EmpName ){  
        this.EmpId = EmpId;  
        this.EmpName = EmpName;  
    }
    static {
       System.out.println("Hello, Java static block initialized.");
       CompanyName = "ProPoint";  // Company Name Changed
    }
    void display(){
     System.out.println("Welcome to "+CompanyName);
     System.out.println("Your Empid is "+EmpId+",Your official name is "+EmpName+
     " & Your Company name is "+CompanyName+".\n");
    }  
}  
public class Company{  
   public static void main(String args[]){
       Emp emp1 = new Emp(40139522,"Meena");  
       Emp emp2 = new Emp(40139524,"Alok");   
       emp1.display();  
       emp2.display();  
   }  
}

Welcome to ProPoint 
Your Empid is 40139522,Your Officia name is Meena & Your Company name is ProPoint.  

Welcome to ProPoint 
 Your Empid is 40139524,Your Officia name is Alok & Your Company name is ProPoint. 

Java Static Classes

A class can only be made static if it is nested. We cannot use the static modifier on top-level classes, but we can use it on nested classes. Such classes are known as Nested static classes. A reference to the Outer class is not required for a nested static class. In this scenario, a static class cannot access non-static Outer class members.

How to declare Java Static Classes

 // Java  program using Static Classes  

class Emp{  
	private static String CompanyName = "DockerTpoint";	
	 static class NestedClass {
		 void display(){
			  System.out.println("Welcome to "+CompanyName);
		  }
           }
}  
public class Company{  
	public static void main(String args[]){
		Emp.NestedClass object=new Emp.NestedClass();
		object.display();
	}  
}

Welcome to DockerTpoint