[Java] Concurrent: Atomic

1. Package
   java.util.concurrent.atomic
   http://developer.android.com/reference/java/util/concurrent/atomic/package-summary.html
   
2. Classes
   java.util.concurrent.atomic provides to atomic access for Boolean, Integer, Long, Reference, their array and reflection-based classes (AtomicXXXFieldUpdater, it is used to enable atomic updates to designated volatile XXX fields of designated classes).
   
3. Sample
• AtomicIntegerFieldUpdater
      import java.util.concurrent.atomic.*; 
       
      class Container { 
        public volatile int no; 
      } 
       
      class Task extends Thread { 
        private AtomicIntegerFieldUpdater updater = 
          AtomicIntegerFieldUpdater.newUpdater(Container.class, "no"); 
        private Container c; 
       
        public Task(Container c) { 
          this.c = c; 
        } 
        @Override 
        public void run() { 
          System.out.println(updater.getAndIncrement(c));   
          System.out.println(updater.getAndIncrement(c));   
        } 
      } 
       
      public class UpdaterUsage { 
        public static void main (String [] args) { 
          Container c = new Container(); 
          Task t1 = new Task(c); 
          Task t2 = new Task(c); 
          t1.start(); 
          t2.start(); 
        }   
      } 
  
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