Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Not only should <code>variable</code> be <code>volatile</code>, but you also want to protect your <code>update</code> function with <a href="http://download.oracle.com/javase/tutorial/essential/concurrency/sync.html" rel="nofollow noreferrer">some sort of synchronization</a> since <code>++variable</code> is not an atomic call. It is, after all, just syntactic sugar for</p> <pre><code>variable = variable + 1; </code></pre> <p>which is not atomic.</p> <p>You should also wrap any calls that read variable in a <a href="http://download.oracle.com/javase/tutorial/essential/concurrency/newlocks.html" rel="nofollow noreferrer">lock</a> of some sort.</p> <p>Alternatively, use an <a href="http://download.oracle.com/javase/1.5.0/docs/api/java/util/concurrent/atomic/AtomicInteger.html" rel="nofollow noreferrer">AtomicInteger</a>. It was made for this sort of thing (for just integer operations).</p> <pre><code>public class A { // initially had said volatile wouldn't affect this variable because // it is not a primitive, but see correction in comments public final AtomicInteger variable; // see comments on this issue of why final public void update() { // Called by one thread constantly variable.getAndIncrement(); // atomically adds one } public int retrieveValue() { return variable.get(); // gets the current int value safely } } public class B { public A a; public void update() { // Called by another thread constantly int v = a.retrieveValue(); // Do algorithm with v... } } </code></pre> <p>For the more complex algorithms, as your recent edit assumes, use synchronization or locks.</p>
    singulars
    1. This table or related slice is empty.
    1. POJava share a variable between two threads
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USjustkt
    1. USjustkt
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COBy saying "some sort of a lock", you mean "put it in a synchronized block or make the method synchronized" isn't it ? Besides, +1 wih the AtomicInteger
      singulars
      1. PO
      1. USRiduidel
    2. COOr use a `java.util.concurrent.Lock` of some sort. I tend to prefer that over `synchronized` for more expressiveness - I like `ReadWriteLock` especially.
      singulars
      1. PO
      1. USjustkt
    3. COYour comment "volatile won't affect this, it's not a primitive" is misleading. It has nothing to do with whether the field is a primative, but everything to do with the fact that `variable` is no longer being reassigned. Making `variable` final would be advised here.
      singulars
      1. PO
      1. USMark Peters
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload