OOPs Interview Questions

title: OOPs Interview Questions description: Object-Oriented Programming interview questions for Java

Q1. OOP ke 4 pillars kya hain?

1. Encapsulation — Data aur methods ko ek unit mein band karna
2. Inheritance — Parent class ki properties child class mein use karna
3. Polymorphism — Ek kaam alag-alag tarike se karna
4. Abstraction — Implementation hide karna, sirf functionality dikhana

Q2. Class aur Object mein difference?

• Class — Blueprint/template hai
• Object — Class ka real-world instance hai

Q3. Constructor kya hai? Types?

Constructor ek special method hai jo object create hone par automatically call hota hai.

• Default Constructor
• Parameterized Constructor
• Copy Constructor

Q4. Method Overloading vs Method Overriding?

Q5. Abstract class vs Interface?

Q6. super keyword ka use?

• Parent class constructor call karna: super()
• Parent class method call karna: super.methodName()
• Parent class variable access: super.variableName

Q7. this keyword ka use?

• Current class instance refer karna
• Constructor chaining: this()
• Method parameter aur instance variable mein confusion avoid karna

Q8. Static aur Instance method mein difference?

• Static method: Class ke sath call hota hai, this nahi hota
• Instance method: Object ke sath call hota hai

Q9. Encapsulation kaise implement karte hain?

• Variables ko private banao
• getter aur setter methods provide karo

Q10. Multiple inheritance Java mein kyun nahi?

Diamond problem ki wajah se. Interface se multiple inheritance possible hai.