Hello reader! The purpose of this article is to simply 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)
• Difference between method overloading VS method overriding
• Object-Oriented Programming: inheritance, polymorphism, abstraction and encapsulation.
• Aggregation and association.
• Dynamic binding (linked to abstraction)
• Static keyword
• Final keyword
• Strings: talk about why they're immutable and what happens in the memory (stack and heap). 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/ 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"?
• 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! 🍀🍀🍀