Interview Questions

Top 5 Java Interview Questions for Freshers

Learning Outcome

5

Distinguish between final, finally, and finalize()

4

Understand the concept of Constructors in Java

3

Compare Array and ArrayList

2

Differentiate between Interface and Abstract Class

1

Explain the difference between JDK, JRE, and JVM

Question 1

JVM vs JRE vs JDK

Think of them as nested layers — each one builds on the next.

💡 Interview Tip:- Remember — JDK ⊃ JRE ⊃ JVM. You need the JDK to write code, but only the JRE to run it.

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Question 2

Array vs ArrayList

Both store collections of data — but they behave very differently under the hood.

Array

• Fixed size — set at creation
• Can store primitives (int, char...)
• Faster performance
• Syntax:

int[] arr = new int[5];

ArrayList

• Dynamic size — grows as needed
• Stores objects only (uses wrappers)
• Part of Collection Framework
• Syntax:

ArrayList<String> list = new ArrayList<>();

Question 3

Interface vs Abstract Class

🔁 Supports multiple inheritance
🧩 All methods are implicitly abstract (pre-Java 8)
🚫 No constructors allowed
📜 Used to define a contract for unrelated classes

1️⃣ Single inheritance only
⚙️ Can have concrete + abstract methods
🏗️ Can have constructors and state
🔗 Used to share code among closely related classes

Question 4

Constructor

Default Constructor

Auto-generated by Java if no constructor is defined. Sets fields to default values.

Rules

Same name as the class. No return type — not even void.

Rules

Same name as the class. No return type — not even void.

Parameterized Constructor

Accepts arguments to initialize fields with specific values at object creation.

A Constructor is a special method that initializes a new object when it's created.

Question 5

final finally finalize()

You've Got This!

You're now equipped with five core Java concepts that interviewers love to test. Review these, practice with real code, and walk into your interview with confidence.