Java Multithreading Interview Questions
Multithreading
and Synchronization is considered as the typical chapter in java programming.
In game development company, mulithreading related interview questions are
asked mostly. A list of frequently asked java multithreading interview
questions are given below.
1) What is multithreading?
Multithreading
is a process of executing multiple threads simultaneously. Its main advantage
is:
- Threads share the same address space.
- Thread is lightweight.
- Cost of communication between process
is low.
2) What is thread?
A
thread is a lightweight subprocess.It is a separate path of execution.It is
called separate path of execution because each thread runs in a separate stack
frame.
3)What is the difference between preemptive scheduling and
time slicing?
Under
preemptive scheduling, the highest priority task executes until it enters the
waiting or dead states or a higher priority task comes into existence. Under time
slicing, a task executes for a predefined slice of time and then reenters the
pool of ready tasks. The scheduler then determines which task should execute
next, based on priority and other factors.
4) What does join() method?
The
join() method waits for a thread to die. In other words, it causes the
currently running threads to stop executing until the thread it joins with
completes its task.
5) What is difference between wait() and sleep() method?
|
wait()
|
sleep()
|
|
1)
The wait() method is defined in Object class.
|
The
sleep() method is defined in Thread class.
|
|
2)
wait() method releases the lock.
|
The
sleep() method doesn't releases the lock.
|
6) Is it possible to start a thread twice?
No,
there is no possibility to start a thread twice. If we does, it throws an
exception.
7) Can we call the run() method instead of start()?
yes,
but it will not work as a thread rather it will work as a normal object so
there will not be context-switching between the threads.
8) What about the daemon threads?
The
daemon threads are basically the low priority threads that provides the
background support to the user threads. It provides services to the user
threads.
9)Can we make the user thread as daemon thread if thread is
started?
No, if
you do so, it will throw IllegalThreadStateException
10)What is shutdown hook?
The
shutdown hook is basically a thread i.e. invoked implicitely before JVM shuts
down. So we can use it perform clean up resource.
11)When should we interrupt a thread?
We
should interrupt a thread if we want to break out the sleep or wait state of a
thread.
12) What is synchronization?
Synchronization
is the capabilility of control the access of multiple threads to any shared
resource.It is used:
- To prevent thread interference.
- To prevent consistency problem.
13) What is the purpose of Synchronized block?
- Synchronized block is used to lock an
object for any shared resource.
- Scope of synchronized block is smaller
than the method.
14)Can Java object be locked down for exclusive use by a
given thread?
Yes.
You can lock an object by putting it in a "synchronized" block. The
locked object is inaccessible to any thread other than the one that explicitly
claimed it.
15) What is static synchronization?
16)What is the difference between notify() and notifyAll()?
The
notify() is used to unblock one waiting thread whereas notifyAll() method is
used to unblock all the threads in waiting state.
17)What is deadlock?
Deadlock
is a situation when two threads are waiting on each other to release a
resource. Each thread waiting for a resource which is held by the other waiting
thread.
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