In which situation the method should be static and when non static?

🧩 When Should a Method Be static?

✅ Use static when:

• The method does not depend on instance variables or objects
• It performs a utility or helper operation
• You want to call it without creating an object
• It’s logically tied to the class itself, not to any specific object

🧪 Examples of static method usage:

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

int result = MathUtils.square(5);  // No object needed

📌 Real Use Cases:

• Utility libraries (e.g., Math.sqrt(), Collections.sort())
• Main method: public static void main(String[] args)
• Factory methods that return instances
• Common functions like validation or formatting

🧩 When Should a Method Be non-static?

✅ Use non-static (instance) methods when:

• The method needs to access instance variables
• Behavior depends on the state of an object
• You need polymorphism (overriding in subclasses)
• Each object may behave differently

🧪 Examples of non-static method usage:

public class Car {
    private String model;

    public Car(String model) {
        this.model = model;
    }

    public void startEngine() {
        System.out.println(model + " engine started.");
    }
}

Car car = new Car("Honda");
car.startEngine();  // Depends on object's model

📌 Real Use Cases:

• Accessing or modifying instance data
• Representing behavior of real-world objects
• Overriding methods in inheritance hierarchies

⚖️ Comparison Table

🧠 Interview-Ready Summary

Use static when the method works independently of object state.
Use non-static when behavior depends on or modifies instance-specific data.