What is Thread in Java with example.

What is Thread in Java with example.



Java Thread is an independent path of execution within a program which can run in parallel with other existing Threads.

Lets try to understand above line with simple scenario and it will be more clear:

Threads in Real time scenario:
Suppose you want to count the population of a India, how will you approach? 

Note: There are 29 states in India.

Approach 1:


First approach is, you start with first state and count population of that state then you will start second state and so on for all 29 states. 
Once you have population of all the states, just sum the population count of all States.

Imagine the time it will take for you to do this as you are alone and you have to count population state by state.
 

Approach 2:

Second approach is, you called 29 people to help you out and you distributed the task of population count to 29 person, each person taking care of individual state. 
  1. Person 1 will take care of population count for State 1. 
  2. Person 2 will take care of population count for State 2 and so on.
Once you have population count of all the states, just sum the population count received from all 29 person and you are done.

Imagine the time it will take for you to do this as compared to Approach 1, surely it will be much less.

So that is what Thread does. In above scenario, you can consider 29 persons as 29 Threads who are doing their respective task of population count.


It is possible that Person 1 may finish population count for State 1 assigned to it much early than Person 2 doing population count for State 2 because State 1 might be small.
Person 2 will continue doing his task even after Person 1 finished early. 


In the similar way, Say If you have 2 Threads say Thread 1 and Thread 2. Thread 1 may complete its job early and Thread 2 will continue doing its job even after Thread 1 is done and they both execute separately. 

Now to relate it with Threads:
When you have task like above that needs to be run in parallel for faster processing at that time Threading will come in picture.

You can say, Java Threads helps creating multiple independent path of execution within a program which can run parallely.
Application Example: 
In Java, when a program requires more than one task to execute in parallel, say for example, 
  1. Reading a data from a local file.
  2. Reading a data from remote connection.

When both of above task need to be executed in parallel at that time Threading will come in picture.
So Java Threads helps creating multiple independent path of execution within a program which can run in parallel.

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Enjoy !!!! 

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