CODEWITHSUNDEEP
javamultithreadinglocking
fredcrs
fredcrs

Reputation: 3621

Will this code not result in a deadlock? Java Threads locking

So the thing is, I want to be able to do this with my class.

object.lockAccess(); object.doSomething(); object.doAnotherThing(); object.doAnotherThingYet(); object.unlockAccess();

So the other thread will not be able to access my class methods while locked. Here is the implementation I did, I was wondering if someone got a better idea, or if it may fail.

private boolean locked = false;

public void lockAccess() throws Exception
{
    while(!tryToLock())
    {
        Thread.sleep(1000);
    }
}

public void unlockAccess() throws Exception
{
    while(!tryToUnlock())
    {
        Thread.sleep(1000);
    }
}

private synchronized boolean tryToLock()
{
    if(locked)
        return false;
    else
    {
        locked = true;
        return true;
    }
}

private synchronized boolean tryToUnlock()
{
    if(locked)
        return false;
    else
    {
        locked = false;
        return true;
    }
}

Upvotes: 0

Views: 127

Answers (3)

Jonathan
Jonathan

Reputation: 13624

Your tryToUnlock() method is incorrect, but otherwise it would technically work.

Most Java programmers would do something more like this, though:

synchronized (object) {
    object.doSomething();
    object.doSomethingElse();
    ...
}

Upvotes: 3

edA-qa mort-ora-y
edA-qa mort-ora-y

Reputation: 31911

Based on your intent it'd be far easier to just do this (since you can use any object as a mutex in Java):

synchronized( object ) {
  object.doSomething(); 
  object.doAnotherThing(); 
  object.doAnotherThingYet();  
}

If you need finer control, and a tryLock in particular, then look at the "Lock" interface and the classes that implement it.

Upvotes: 3

Thilo
Thilo

Reputation: 262724

while(!tryToLock())
    {
        Thread.sleep(1000);
    }

Terrible idea.

Use a Lock implementation from java.util.concurrent.

Or just a synchronized block.

Upvotes: 4

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