Java Repository: Most frequently asked Java Interview Questions

This is a sample from my recent round of Java interviews:

String questions: Check if one string is a rotation of other string, check if a string is a palindrome, check if a string is a substring of other string, return the index of the first occurence of a substring in other string, reverse a string, Difference between StringBuilder, StringBuffer and String
LinkedList questions: Reverse a linked list recursively(in-place) and iteratively, delete a node from linked list, find the nth node, find the nth node from the end, test if a linked list has a cycle, write test cases
What is immutable, Implement an immutable class (e.g. myDateTime)

What are volatile, synchronized, atomic
What are some ways to implement a singleton in Java
Implement a counting semaphore
JVM/GC questions
Checked vs unchecked exceptions, finalize
What is a queue, stack, heap
Level-order BFS on a binary tree
What happens in the system during a recursive call
Remove an item from an array of ints, print the second largest number in an array, remove a character from a string
Write a method receiving a stream of integers, caching the last 10 min of data and returning a number if it's less than the current input
Mutexes, ReadWriteLock, ConcurrentHashMap, ArrayBlockingQueue, Thread pools, LinkedList vs ArrayList, Object Pooling, Read-Modify-Write, java.util.concurrent, java.util.concurrent.atomic, CAS, Collections, ADT, Java 5 Generics
HashMap vs HashTable vs ConcurrentHashMap
Synchronous vs asynchronous, thread contention, race conditions/deadlocks and how to prevent/debug them, thread confinement, cache coherence, false sharing, cache lines
How would you write a socket client/server in Java
Java IO/NIO, socket multiplexing, blocking vs non-blocking, select/epoll
Sleep vs wait
Process vs thread, Java threads vs Pthreads, Linux threads vs Solaris threads, what happens when a process/thread is started/terminated, what happens during context switch
Java Memory Model, Weak references
Jini, JMS, Javaspaces, JGroups, Hibernate trivia
Abstract Class vs Interface
Memoization, give an example
Can you have a protected method in Interface
How to force a stop-of-the-world GC
What can be done to interrupt a synchronized method that is blocked
Java performance, heap profiling, GC tuning, thread dumps, Hotspot vs JRockit
How would you implement low latency data structures
How would you debug performance issues, what do you do if a database query is "slow", describe the troubleshooting approach when a customer complains that the UI is "slow"
Knight Tour puzzle- write a method for a knight to find another figure (a fool) on a chessboard
Clock puzzles - find the angle between hr,min,sec handles, etc
3 jars puzzle (one jar is filled with 8 gallons, two jars are empty (capacity 5, 3), write a routine to get to 4-4 state
Inner join vs outer join
What are ACID properties in a database
What is caching; How would you implement a caching server for a streaming video service (messaging/queues, data structures, expiration/eviction), how would you benchmark the performance of your broadcasting/caching server/service, how do you scale it to thousands of customers, what is CDN
How would you design a high throughput order management system, matching engine, market data engine, FIX engine (trading)
How would you design a data collection service (i.e. downloading/streaming data from multiple sources from the web), distributed data feeds/CRUD data store design,indexing, performance/scalability/availability considerations
What is the fastest way to do a grep on 10GB plain text file on a laptop
Describe the projects you're most proud of, the most difficult problems you've solved as an engineer, what is your favorite programming language