Language Basics

Language Knowledge check

• What is the difference between method overloading and method overriding in Java, and where would you use each?

• Explain the difference between final, finally, and finalize in Java?

• Explain the difference between a shallow copy and a deep copy in Java?

• Hashcode and equals contract

• Immutable class design it.

Interface and Abstract class

• Diamond problem and types of inheritance.

• Explain what they are and difference between them.

• Scenario based questions

Lambda

• What is default method in lambda?

• How many methods can be abstract methods in lambda?

• What does "effectively final" mean in lambda expressions.

Java 8 features

• Explain the use of Optional in Java 8 and how it helps handle NullPointerException.

Collections

• What is the difference between HashMap and ConcurrentHashMap in Java.

• How does HashMap work, when we do put and get operation.

• Does ConcurrentHashMap acquire lock when reading the data?

Streams

• Explain the difference between terminal and intermediate operations in Java Streams with examples.

• How does parallel stream work bts?

Concurrency

• What is a thread, what are its different states?

• How does wait and notify/notigyAll work?

• What is race condition?

• What is volatile?

• What is happens-before relationship?

• Difference between synchronized method and block?

• Can you explain the Re-entrant lock?

• What is difference between callable and runnable?

• What is completeable future? How does it work?

• What is dead lock and livelock?

Framework

• Explain Executor service?

• Explain how fork join pool work?

Technique

• How to stop a thread?

Internals

• Java Memory Model

• Java Memory layout

• Java GC and its types

New Features

Java 9

Java 10

Java 11

Java 12

Java 13

Java 14

Java 15

Java 16

Java 17