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Is run Method is only way to achieve Multi Threading [closed]

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I want to run simultaneously two different methods in two different classes
Is run method is the only way?
If it is Why??

Your code snippet does not show how you actually start these threads, I am assuming something like new Thread2().start(). What this does is create a new thread and the new thread proceeds (in the background) to execute its run method (and then terminates when that method returns).
Every thread runs code that is contained with a run() method. That is just how threads work. There has to be some convention to let the JVM know where the code for the thread is.
From within that method, you can call any other method on any other object that you have access to.

java multithreading method that can acess atmost 3 threads concurrently [closed]

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Hi today in interview they asked a multi threading question that create a procedure in which there is a method getDBConnect() so that atmost 3 threads can access it concurrently. if 4th thraed try to access getDBConnect() method then 4th thread will go on wait state if anyone of 3 thread release the method getDBConnect() then 4th thread will access the getDBConnect() method using simple thread or executor thread.
Please help me to understand how can i make program of multi threading so that above criteria should be satisfied.

I'm not going to write code for you. But I can hint what this question is about. There is very interesting primitive of multithreading synchronization called Semaphore. JDK contains detailed description and sample of use https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/Semaphore.html

One thread for each mob in a 2D game: Will it be system-resource consuming? [closed]

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I'm developing a java 2D game, with a Board class and Mob(s) class. The board class has a thread that calls 'repaint()' every a specified delay, while the mobs class constructs a new thread for each of the mob spawned, which means when it does something, it ticks its time on its own. Simply said, I seperate the thread to enable frame rate setting. So i just need to only set how long does the Board thread sleep, like faster sleep means more frame rate (I use threads for this because a site says threaded timing can be made real precise). But then it means in a crowded in-game situation there would be a lot of thread running from every active Mob there.
My question: if i have this lots of thread running at the same time, wouldn't it be consuming a lot of system resources? And if yes, what is the best way round so I don't need to use threads? (just to note 2D game "crowded" situation can be "really crowded").

I think your question could resume to one of these :
Why is creating a Thread said to be expensive?
How expensive is creating of a new thread in Java? When should we consider using of a thread pool?
Is it expensive to create the Thread object or to actually start the thread?
etc...
Plenty of resource to find info on the subject.
what is the best way round so I don't need to use threads
This question is not appropriate for SO (too broad)

print stack with changing values with Thread [closed]

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How can I know when the thread was stoped and the processor moves to another thread..
Transition between threads harms my calculations, there is some way to know if the thread left and returned to my function?

You can not know when your thread was stopped and the system rescheduled another thread.
But - you can minimize the number of times this event happens by setting the affinity of your thread to one of the processors, and the affinities of the other threads to the other processors.
If you are using Linux, you can use taskset for each thread in the system (get the list by "ps -e") to set the affinities of the other threads to other processors.
This will decrease the load on the processor and will cause it to context-switch less times.

The simple answer is - you can't. Even if you could detect thread context switches it happens far too often to usefully logged.
A better question would be to look at why you need to know. If there is a problem there post it as a question and we can solve the real issue.

Does fork() call compute eventually? [closed]

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My understanding is that it creates another thread and runs compute() in another thread.
then join fetches the result once recursively got it.
I would like to know whether fork() calls compute() or not. Thanks in advance.

The fork method will not call compute. It will push the forked task to a work queue in which the running thread determines if it should eventually call compute itself or notify other threads to steal that task and invoke compute.