Question

In formal terms, a monitor is an object which only allows one of its methods to be executed at once.

For Java:

1) How could you implement a class satisfying the monitor’s fundamental mutual exclusion property – that is, a class whose instantiated objects ensured mutual exclusion among their methods? Provide a code fragment as an example.

2) Could you mutually exclude critical sections smaller than an entire method without resorting to mutex locks? If so, how?

3) How would you implement condition variables as we described them in class? Provide a code fragment as an example.

4) Does the implementation differ if you need more than one condition variable? If so, how?

Answer 1

Q1  implementing a class satisfying the monitor’s fundamental mutual exclusion property is by synchronized in java

we can write synchronized function

public synchronized void funcA(Object a ){

// code of the function

}

so if two thread access at same time only one thread will be able to execute it and other thread will wait

Q2 java also provide synchronized blocks

eg void funcA(object a)

{

synchronized(a){

// critical section of the code

}

}

Q3 to implement condition variable

public synchronized void func(object a)

{

// here we want to wait untill the value of any condition variable is false

whiile(isval == true)

{

a.wait();

}

}

in the above code our code will not execute and will be in waiting state untill the value of the variable isval is true;

Q4 the implementation will differ if there are multiple condition variable.

then there will be more condition which are to be checked in our code