CODEWITHSUNDEEP
javaandroidmultithreading
webshaker
webshaker

Reputation: 467

Java [android]: should I used synchronized ou semphore object?

I have 2 threads.

The first one calls this function

public int doCompute1(obj)
{
    if (obj.state == OK_FOR_COMPUTE1)
    {
      // do something
      obj.state = OK_FOR_COMPUTE2;
    }
}

The second thread calls this function

public int doCompute2(obj)
{
    if (obj.state == OK_FOR_COMPUTE2)
    {
      // do something
      obj.state = OK_FOR_COMPUTE1;
    }
}

For the moment it seems to work perfectly !

My question is: Is it correct ? Is it possible that on multicore processor, obj.state is in cache memory and then modifiyng this vaue by a thread, wouldn't be visible by the second thread?

What should I do if this code is not correct?

Upvotes: 0

Views: 113

Answers (1)

VinceFR
VinceFR

Reputation: 2571

synchronized(obj){  
    if (...){ 
    }
}

will do the stuff

EDIT:

What synchronized do?

synchronized(obj){  //if obj is not locked,i lock it and go to the if instruction.if obj is locked, i'm waiting for its unlocking

          //some stuff that will run with no thread-interruption caused by other synchronized block locked on the obj object 

    }//the obj object is unlocked and let other methods enter their synchronized(obj) block

Upvotes: 2

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