What is the use of the static keyword in Java

💡 Concept: Static Keyword in Java

The static keyword is used to create class-level variables and methods that belong to the class rather than instances.

📘 Quick Intro

Static members are shared across all instances of a class and can be accessed without creating an object.

🧠 Analogy

Think of static members as shared tools in a workshop: everyone uses the same hammer instead of having individual ones.

🔧 Technical Explanation

Static variables: Shared among all instances.
Static methods: Can be called without an object.
Static blocks: Used for static initialization.
Static nested classes: Nested classes declared static.
Useful for utility or helper methods and constants.

🎯 Use Cases

✅ Define constants with static final.
✅ Utility methods like Math.sqrt() are static.
✅ Maintain counters shared across instances.

💻 Java Static Keyword Example


class Counter {
    static int count = 0;

    Counter() {
        count++;
    }

    static void displayCount() {
        System.out.println("Count: " + count);
    }
}

public class Main {
    public static void main(String[] args) {
        new Counter();
        new Counter();
        Counter.displayCount(); // Count: 2
    }
}

❓ Interview Q&A

Q1: What does static mean in Java?
A: Belongs to class, not instance.

Q2: Can static methods access instance variables?
A: No.

Q3: When are static blocks executed?
A: When class loads.

Q4: Can static methods be overridden?
A: No, they are hidden.

Q5: What is a static nested class?
A: Nested class declared static.

Q6: Are static variables thread-safe?
A: No, need synchronization.

Q7: Can you access static members without object?
A: Yes.

Q8: Can static variables be final?
A: Yes, constants.

Q9: Difference between static and instance variables?
A: Static shared; instance per object.

Q10: Use of static keyword?
A: Class-level shared members.

📝 MCQs

Q1. What does static mean in Java?

Belongs to instance
Belongs to class, not instance
Both
None

Q2. Can static methods access instance variables?

Yes
No
Sometimes
Depends

Q3. When are static blocks executed?

At runtime
When class loads
When object created
Never

Q4. Can static methods be overridden?

Yes
No
Sometimes
Depends

Q5. What is a static nested class?

Inner class
Nested class declared static
Anonymous class
None

Q6. Are static variables thread-safe?

Yes
No
Sometimes
Always

Q7. Can you access static members without object?

No
Yes
Sometimes
Depends

Q8. Can static variables be final?

No
Yes
Sometimes
Depends

Q9. Difference between static and instance variables?

Same
Static shared; instance per object
Instance shared
None

Q10. Use of static keyword?

Instance members
Class-level shared members
Local variables
None

💡 Bonus Insight

Static keyword enables shared resources and utility methods without creating objects, important for memory efficiency and design.

📄 PDF Download

Need a handy summary for your notes? Download this topic as a PDF!

📄 PDF Download Coming Soon