[concurrency-interest] Locking on local variables

Sleiman Jneidi jneidi.sleiman at gmail.com
Fri Jan 15 10:21:47 EST 2016


Hi everyone,

>From what I know, locking on local variables is useless, Brian Goetz in his
book gave the following as an example of a bad lock

 synchronized(new Object()){
  ..
 }

So I assume, the code above is equivalent to the following

  Object o = new Object();

 synchronized(o){
  ..
 }

However looking at ConcurrentHashMap#computeIfAbsent I see the following

Node<K,V> r = new ReservationNode<K,V>();
    synchronized (r) {
    ...
    }

Just curious, why is that?


Thanks
Sleiman
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