Do You know Java Keyword static?

In Java, the static keyword can be applied to variables, methods, code blocks, and nested classes.

1. static Variables (Class Variables)

A static variable belongs to the class rather than to any specific object. All instances of the class share the same static variable.

• Static variables are initialized when the class is loaded and only one copy is stored, shared by all instances.
• They can be accessed using ClassName.variableName, such as Example.count.

Example:

class Example {
    static int count = 0; // Static variable

    Example() {
        count++;
    }

    public static void main(String[] args) {
        Example obj1 = new Example();
        Example obj2 = new Example();
        System.out.println(Example.count); // Output: 2
    }
}

2. static Methods

A static method belongs to the class and can be called directly without creating an instance of the class.

• A static method can only access static variables and other static methods; it cannot directly access instance variables.
• It cannot use the this or super keyword.

Example:

class MathUtil {
    static int square(int x) {
        return x * x;
    }

    public static void main(String[] args) {
        System.out.println(MathUtil.square(5)); // Output: 25
    }
}

3. static Blocks (Static Initialization Blocks)

A static block executes once when the class is loaded, usually for initializing static variables.

• Executes only once when the class is loaded.
• Executes before the constructor.

Example:

class StaticBlockExample {
    static int value;

    static {
        value = 10;
        System.out.println("Static block executed");
    }

    public static void main(String[] args) {
        System.out.println("Value: " + value); // Output: 10
    }
}

4. static Nested Classes

A static nested class does not depend on an instance of the outer class and can be instantiated directly.

• A static nested class can access static members of the outer class but cannot access non-static members.

Example:

class Outer {
    static class Inner {
        void display() {
            System.out.println("Inside static nested class");
        }
    }

    public static void main(String[] args) {
        Outer.Inner obj = new Outer.Inner();
        obj.display(); // Output: "Inside static nested class"
    }
}

5. Importance of static in the main Method

The main method in Java must be static because the JVM calls it without creating an object of the class.

• Since the JVM executes main without creating an object, it must be static to allow direct execution.

Example:

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
    }
}

6. Summary

The static keyword is essential in Java and can improve efficiency and structured program design when used correctly.