Java Interview Questions

Java Interview Questions

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2 min read

Hello reader! The purpose of this article is to share some common java interview questions that I was asked in the past when going through job interviews with top financial firms. I hope that you'll find this useful.

  • What is a class?

  • What is an object?

  • Object VS class

  • Method overloading.

  • Method overriding.

  • Access modifiers (private, public, protected, default).

  • The difference between method overloading and method overriding.

  • Object-Oriented Programming: inheritance, polymorphism, abstraction and encapsulation.

  • Aggregation and association.

  • Dynamic binding (linked to abstraction).

  • Static keyword.

  • Final keyword.

  • Strings: discuss why they're immutable and what happens in the memory (stack and heap). The string is a class.

  • Stringbuilder VS Stringbuffer.

  • Interface: why it's used.

  • Can we have multiple inheritance? If not, why? What can we do instead?

  • Difference between abstract class and interface.

  • Memory management: garbage collection, the types of garbage collectors.

  • How does a hashmap work internally?

  • Collections Framework.

  • Exception handling: throw, throws keywords, what is a runtime exception.

  • Runtime Type Checking.

  • Difference between the keywords final, finally, finalize.

  • try...catch block.

  • Finally block.

  • Exception propagation.

  • Multithreading: what is a thread, how to create a thread (Runnable interface OR Thread class).

  • Thread safety.

  • Synchronize.

  • Difference between a set and a list.

  • Java 11 features.

  • JDK, JRE, JVM.

  • SOLID Principles.

  • Test-Driven Development.

  • Git commands.

  • What does "unboxing" mean?

  • Is Java "pass-by-value" or "pass-by-reference"?

  • How do you return multiple values in Java?

  • What does "covariance" mean?

Related: Java Phone Interview Questions - Beginner Level

Good luck! ๐Ÿ€๐Ÿ€๐Ÿ€

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