Java Threading/ Multithreading Interview Questions with Answers

Describe synchronization in respect to multithreading.

Ans: With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchonization, it is possible for one thread to modify a shared variable while another thread is in the process of using or updating same shared variable. This usually leads to significant errors.


Explain different way of using thread?

Ans: The thread could be implemented by using runnable interface or by inheriting from the Thread class. The former is more advantageous, 'cause when you are going for multiple inheritance..the only interface can help.


What are the two types of multitasking?

Ans :

1.process-based

2.Thread-based

What are the two ways to create the thread?

Ans :

1.by implementing Runnable

2.by extending Thread

What is the signature of the constructor of a thread class?

Ans : Thread(Runnable threadob,String threadName)

What are all the methods available in the Runnable Interface?

Ans : run()

What is the data type for the method isAlive() and this method is available in which class?

Ans : boolean, Thread

What are all the methods available in the Thread class?

Ans :

1.isAlive()

2.join()

3.resume()

4.suspend()

5.stop()

6.start()

7.sleep()

8.destroy()

What are all the methods used for Inter Thread communication and what is the class in which these methods are defined?

Ans :

1. wait(),notify() & notifyall()

2. Object class

What is the mechanisam defind by java for the Resources to be used by only one Thread at a time?

Ans : Synchronisation

What is the procedure to own the moniter by many threads?

Ans : not possible

What is the unit for 1000 in the below statement?

ob.sleep(1000)

Ans : long milliseconds

What is the data type for the parameter of the sleep() method?

Ans : long

What are all the values for the following level?

max-priority

min-priority

normal-priority

Ans : 10,1,5

What is the method available for setting the priority?

Ans : setPriority()

What is the default thread at the time of starting the program?

Ans : main thread

The word synchronized can be used with only a method.

True/ False

Ans : False

Which priority Thread can prompt the lower primary Thread?

Ans : Higher Priority

How many threads at a time can access a monitor?

Ans : one

What are all the four states associated in the thread?

Ans : 1. new 2. runnable 3. blocked 4. dead

The suspend()method is used to teriminate a thread?

True /False

Ans : False

The run() method should necessary exists in clases created as subclass of thread?

True /False

Ans : True

When two threads are waiting on each other and can't proceed the programe is said to be in a deadlock?

True/False

Ans : True

Which method waits for the thread to die ?

Ans : join() method

Which of the following is true?

1) wait(),notify(),notifyall() are defined as final & can be called only from with in a synchronized method

2) Among wait(),notify(),notifyall() the wait() method only throws IOException

3) wait(),notify(),notifyall() & sleep() are methods of object class

1
2
3
1 & 2
1,2 & 3
Ans : D

Garbage collector thread belongs to which priority?

Ans : low-priority

What is meant by timeslicing or time sharing?

Ans : Timeslicing is the method of allocating CPU time to individual threads in a priority schedule.

What is meant by daemon thread? In java runtime, what is it's role?

Ans : Daemon thread is a low priority thread which runs intermittently in the background doing the garbage collection operation for the java runtime system.