Java Interview Guide: How to Build Confidence With a Solid Understanding of Core Java Principles pdfdrive com

ThreadLocal Storage
The ThreadLocal class allows values to be stored inside of the currently
running Thread object. For example, imagine tracing an HTTP request that
starts in a servlet and traverses through a service. Rather than pass a transaction
id as an argument in every method, you could instead store the id in
a ThreadLocal object and retrieve it statically along the way.
ThreadLocal
variables reduce the verbosity of methods, but care must
be taken to ensure that a value is removed if the thread is returned
to a thread pool.

---

Atomic Variables
Java introduced several variables with built-in concurrency such
as AtomicInteger, AtomicLong, and AtomicBoolean. For example,
an AtomicInteger could replace and even outperform our Counter class
because it’s implemented with native method calls. A native method call
executes outside of the JVM in a platform-dependent programming language.

---

Questions
What is the lifecycle of a Thread?
Why is synchronization necessary on shared resources?
What is used as a lock for synchronized static and synchronized non-
static methods?
What would happen if two different threads hit two synchronized non-static
methods on the same object simultaneously?
What would happen if two different threads hit a synchronized static method and
synchronized non-static method on the same object simultaneously?
What one thing does the volatile keyword guarantee about a variable?
What two things does the synchronize keyword guarantee about a block of code?
What are some built-in concurrent data structures?
What is the executor framework?
What is a ThreadLocal variable?
What are atomic variables?

---