static Keyword in Java

"static" Keyword in Java

Introduction

static keyword is a non-access modifier in Java.
It is used to create members (variables, methods, blocks or nested classes) that belong to the class rather than any specific object.
We don't need to create an object to access a static member — we can access it using the class name directly.
Use of static keyword:
- It is used for memory management by sharing data among all instances of a class.
- It means a static member is shared among all objects of the class.

1. Static Variable (Class Variable):

A static variable is shared among all objects of a class.
It is initialized only once, at the start of program execution.
Useful for defining common properties or counters.

Java Program Example 1:

class Student
{
    String name;
    int rollNo;
    static String schoolName = "ABC Public School";  // static variable shared by all students

    // Constructor
    Student(String name, int rollNo)
    {
        this.name = name;
        this.rollNo = rollNo;
    }

    // Method to display student details
    void displayDetails()
    {
        System.out.println("Name     : " + name);
        System.out.println("Roll No  : " + rollNo);
        System.out.println("School   : " + schoolName);
        System.out.println("--------------------------");
    }
}

public class StaticDemo
{
    public static void main(String[] args)
    {
        // Creating student objects
        Student s1 = new Student("Amit", 101);
        Student s2 = new Student("Deepak", 102);
        Student s3 = new Student("Rahul", 103);

        // Displaying student details
        s1.displayDetails();
        s2.displayDetails();
        s3.displayDetails();
    }
}

Output:

Name     : Amit
Roll No  : 101
School   : ABC Public School
--------------------------
Name     : Priya
Roll No  : 102
School   : ABC Public School
--------------------------
Name     : Rahul
Roll No  : 103
School   : ABC Public School
--------------------------

Java Program Example 2:

public class Counter
{
    // static variable to keep count of objects
    static int count = 0;

    // Constructor
    Counter()
    {
        count++;  // Increment static counter
        System.out.println("Object created. Count = " + count);
    }

    public static void main(String[] args)
    {
        // Creating objects
        Counter c1 = new Counter();
        Counter c2 = new Counter();
        Counter c3 = new Counter();
    }
}

Output:

Object created. Count = 1
Object created. Count = 2
Object created. Count = 3

2. Static Method:

A static method belongs to the class, not to any specific object.
It can be called without creating an object of the class.

Java Program Example:

public class StaticDemo
{
    // Static method
    static void greet()
    {
        System.out.println("Hello! This is a static method.");
    }

    // Non-static method
    void showMessage()
    {
        System.out.println("This is a non-static method.");
    }

    public static void main(String[] args)
    {
        // Calling static method directly without creating an object
        greet();

        // Calling non-static method requires an object
        StaticDemo obj = new StaticDemo();
        obj.showMessage();
    }
}

Output:

Hello! This is a static method.
This is a non-static method.

Note:

A static method cannot access non-static (instance) variables or methods directly.
Static methods are often used for utility or helper methods like Math.pow().

3. Static Block:

A static block is used to initialize static variables.
It is executed only once, when the class is first loaded into memory.
It is useful for setting up complex static values.

Java Program Example:

public class StaticDemo
{
    static int maxLimit;
    static
    {
        maxLimit = 100;  // static block for initialization
        System.out.println("Static block executed.");
    }

    public static void main(String[] args)
    {
        System.out.println("Max Limit : "+maxLimit);
        System.out.println("Main method executed");
    }
}

Output:

Static block executed.
Max Limit : 100
Main method executed

4. Static Class (Nested Class):

Java allows the creation of static nested classes (a class inside another class declared as static).
A static nested class can access only static members of the outer class.
It doesn't need an instance of the outer class to be instantiated.

Java Program Example:

public class Outer
{
    // Static nested class
    static class Inner
    {
        void show()
        {
            System.out.println("Static nested class method.");
        }
    }

    public static void main(String[] args)
    {
        // Creating an object of the static nested class
        Outer.Inner obj = new Outer.Inner();
        obj.show();
    }
}

Output:

Static nested class method.

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"static" Keyword in Java

Introduction

1. Static Variable (Class Variable):

Output:

Output:

2. Static Method:

Output:

3. Static Block:

Output:

4. Static Class (Nested Class):

Output:

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