Java Multi Threading

Multi- Threading

What is difference between Process, Procedure and Processors?

* Process is a flow of execution to perform a particular task.

* Procedure is a set of instructions representing a particular task.

* Processor is an Hardware Component generating process to
perform task.

What is difference between process and Thread?

Process is heavy weight, it will take more execution time & more

memory Consumption, it will reduce applications performance.

Thread is light weight, it will take less execution time & less

memory Consumption, it will improve application performance.

What is Multitasking?

Executing several task simultaneously is called multitasking.

Process Based Multitasking -

Executing several tasks simultaneously where each task is separate

independent process such type of multitasking is called process

based multitaksing.

Example: OS Level

Thread Based Multitasking-

Executing several tasks simultanously where each task is a separate

independent part of the same program, is called Thread based

multitasking. And each independent part is called a "Thread".

What is Thread, and how many ways we are able to prepare Thread is in java application?

Thread is a flow of execution, it can be used to perform a particular task.

As per Predefined library provided by java, There are 2 ways to prepare Threads.

i. Extending Thread Class:

In this approach, we have to declare an user defined class and it

must be extended from java.lang.Thread class

Ex: class MyThread extends Thread

{ ---implementation---- }

ii. Implementing Runnable Interface:

In this approach, we have to declare an user defined class it must

implements java.lang.Runnable interface

Ex: class MyThread implements Runnable

{ ---implementation--- }

Thread Scheduler:

If multiple Threads are waiting to execute then which Thread will execute 1st is decide by "Thread Schedular" Which is part of JVM.

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.

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.

Explain Thread class constructors?

There are eight constructors are available in Thread class:

1. Thread t=new Thread();
2. Thread t=new Thread(Runnable r);
3. Thread t=new Thread(String name);
4.Thread t=new Thread(Runnable r, String name);
5.Thread t=new Thread(ThreadGroup g, String name);
6.Thread t=new Thread(ThreadGroup g, Runnable r);
7.Thread t=new Thread(ThreadGroup g, Runnable r, String name);
8.Thread t=new Thread(ThreadGroup g, Runnable r, String name, long stacksize);

What is Daemon Thread? And give an example?

The Threads which are running in the background are called
Daemon Thread.

Example: Garbage collector.

What is the purpose of a Daemon Thread?

The main purpose of Daemon Threads is to provide support for

non-daemon Threads.

How we can check Daemon nature of a Thread?

We can check Daemon nature of a Thread by using

isDaemon() method.

Is it possible to change a Daemon nature of a Thread?

Yes, we can change Daemon nature of a Thread by using setDaemon() method.

Is main thread is Daemon or non-daemon?

By default main thread is always non-daemon nature.

Once we created a new thread is it daemon or non-daemon.

Once we created a new Thread, The Daemon nature will be inheriting from parent to child.

If the parent is Daemon the child is also Daemon and if the parent is non-daemon then child is also non-daemon.

What is the difference between synchronized method and static synchronized method?

If a Thread wants to execute a synchronized method first it has to get the lock of the object.

Once a Thread got the lock then it is allow to execute any synchronized method on that object.

If a Thread wants to execute static synchronized method that Thread has to get class level lock once a Thread got class level lock then only it is allow to execute static synchronized method.

Explain life cycle of a Thread?

1.New / Born : When we Create Thread Class object in java applications automatically Thread will come to New / Born State.

2. Runnable State : When we access start( ) method and before assigning system resources like memory and time stamp then Thread is available in Runnable state.

3. Running State : When System resources are assigned to a Thread after calling start() method then that thread is available in Running State.

4. Blocked State : When we access sleep( ) method with a particular time duration, when we access wait( ) method, suspend( ) method and when we perform IO Operations then automatically the respective thread will come to Blocked State.

In java application , Thread will come from Blocked state to Runnable state, When sleep time is completed , if any other Thread accessing notify( ) or notifyAll( ) method or resume( ) method and When IO Operations are completed.