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static keyword

In Java, the `static` keyword is used to declare members (variables and methods) that belong to the class rather than to instances of the class. When a member is declared as static, it means that there is exactly one copy of that member shared by all instances of the class. The `static` keyword can be applied to variables, methods, and nested classes. Here's a breakdown of how `static` is used:


1. Static Variables (Class Variables):

   public class MyClass {

       // Static variable

       static int count;


       public MyClass() {

           // Incrementing the static variable in the constructor

           count++;

       }

   }


   In the example above, `count` is a static variable, and its value is shared among all instances of the `MyClass`.


2. Static Methods:


   public class MathUtils {

       // Static method

       public static int add(int a, int b) {

           return a + b;

       }

   }


   The `add` method in the `MathUtils` class is declared as static. It can be called using the class name (`MathUtils.add(2, 3)`) without creating an instance of `MathUtils`.


3. Static Blocks:

   public class Configuration {

       // Static block

       static {

           // Initialization logic

           System.out.println("Initializing configuration...");

       }

   }


   Static blocks are used for static initialization. They are executed when the class is loaded, and they run before the execution of any static method or the creation of any static variable.


4. Static Nested Classes:

   


   public class OuterClass {

       // Static nested class

       static class NestedClass {

           // ...

       }

   }


   A static nested class is associated with its outer class rather than instances of the outer class. It can be instantiated without creating an instance of the outer class.


Key Points:


- Static members belong to the class, not to instances.

- Static members can be accessed using the class name.

- Static methods can only directly call other static methods or access static variables.

- Static members are loaded when the class is first accessed (loaded) by the Java Virtual Machine (JVM).


Here's an example demonstrating the use of static variables and methods:


public class StaticExample {

    // Static variable

    static int instanceCount = 0;


    // Instance variable

    int instanceNumber;


    public StaticExample() {

        // Incrementing instanceCount in the constructor

        instanceCount++;

        // Assigning instanceCount to instanceNumber

        instanceNumber = instanceCount;

    }


    // Static method

    public static void printInstanceCount() {

        System.out.println("Number of instances: " + instanceCount);

    }

}


class Main {

    public static void main(String[] args) {

        // Creating instances of StaticExample

        StaticExample obj1 = new StaticExample();

        StaticExample obj2 = new StaticExample();


        // Accessing static variable using class name

        System.out.println("Accessing static variable: " + StaticExample.instanceCount);


        // Accessing instance variable

        System.out.println("Instance number for obj1: " + obj1.instanceNumber);

        System.out.println("Instance number for obj2: " + obj2.instanceNumber);


        // Accessing static method using class name

        StaticExample.printInstanceCount();

    }

}

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