Core Java

Core Java - OOP Concepts, Garbage Collection, Multi-threading, Collections Framework, Java 8 Features, Lambda Functions, Streams.

Core Java - OOPS, Inheritance, Garbage Collection, multi-threading & Concurrency, Java Collections framework.

Whats New

  1. Whats new in Java 9

  2. Whats new in Java 8

  3. Whats new in Java 7

  4. Whats new in Java 6

Garbage Collection

  • How does Mark and Sweep Work?

  • What are different Memory generations in java?

  • How will you troubleshoot Memory Issues in a Java application running in production?

Multi-threading and Concurrency in Java

  • Threading Jargons in java

  • What is Java Memory Model?

  • What is Producer Consumer Problem

  • What is Non Blocking Algorithm? What is CAS?

  • Explain Internals of Concurrent HashMap

  • What is use of CopyOnWriteArrayList?

  • What is Volatile Variable?

  • What is ThreadLocalRandom? when should one use it over Random?

  • What is Dead Lock in Java, how will you detect a dead lock in a given application? What steps you will take to avoid the deadlock situation?


  • What are Immutable Objects? What is benefit of it?

  • What is Executors?

  • What is Thread Pool? How will you implement a basic thread pool from scratch?

  • What is Fork Join?

  • How are Concurrent Collections different from Normal Collections?

  • What is a Blocking Queue?

  • What is difference between ArrayBlockingQueue, DelayQueue and LinkedBlockingQueue in Java?

  • What is Semaphore?

  • What is CountDownLatch?

  • What is ThreadLocal Object? Give a example of its use?

  • What is CompletionService or ExecutorCompletion Service? Give a practical use case.

  • What is special about classes present in concurrent.atomic package? What is CAS?

  • What is Stamped Lock introduced in Java 8?

  • There are 3 different threads in a single method, how will you make then run sequentially?

Java Collections Framework

  • ArrayList vs Vector?

  • What is difference between Hashmap and ConcurrentHashMap?

  • What is red-black-tree?

  • What is MinHeap?

  • What is Merge Sort? Which Sorting is used by Java Collections.sort() internally?

Coding Problems for Core Java

  • Write a simple Java program which will print Fibonacci series

  • Write a Program that calculates Prime Numbers in Java.

  • Write a program to check if a given String is Palindrome

  • Write a Program to check if given number is Armstrong number *

Design Problems

  • Implement a Basic Token Bucket Algorithm in Java

  • Design and Implement a File Storage for millions of files. Consider that not more than 1000 files should be placed inside a single directory.

  • Implement a Web Crawler algorithm using Java

  • Design a Vending Machine in Java

Books and References

  • Head First Design Patterns

  • Head First Object Oriented Design and Analysis

  • Concurrency In Practice by Biran Goetz

  • Effective Java 2nd Edition

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