Question

Let say that I create an object and run it in a thread, something like this.

public class Main {

public static void main(String[] args) {
    SomeClass p = new SomeClass (143);
    p.start();
    p.updateNumber(144);

}}

Is it possible to update the parameter passed in SomeClass with a methode updateNumber() as fallows:

# Updated

class SomeClass extends Thread {
     volatile int number ;
     SomeClass (int number ) {
         this.number = number ;
     }

     public void run() {
         while(true){
          System.out.println(number);
           }
     }

  public  void updateNumber(int n){     
          number =n;
          }
  }   

Result :
144
144
144
144
144
…

Thanks

Answer 1

One other option not mentioned and which is the option you should use instead of synchronization as mentioned above is the make use of the Concurrency package introduced by Doug Lee in Java 1.5.

Use the Atomic classes, these take care of all you concurrency woes. (well to a point)

Something like this:

 private AtomicInteger number = new AtomicInteger(0);

 public void updateNumber(int n) {
   number.getAndSet(n);
 }

 public int getNumber() {
   return number.get();
 }

Java 1.6 AtomicInteger JavaDoc

Java Concurrency in Practice

In my opinion the Java Concurrency in Practice is the best book on threading in Java