一个使用AtomicInteger完成的Java线程同步的例子

package thread;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
public class AtomIntTest {
  private AtomicInteger atomicI = new AtomicInteger(0);
  private int i = 0;
  private int unsafe = 0;
  public static void main(String[] args) {
    final AtomIntTest cas = new AtomIntTest();
    final int TOTAL_THREAD_NUM = 10;
    List<Thread> ts = new ArrayList<Thread>();
    long start = System.currentTimeMillis();
    for (int j = 0; j < TOTAL_THREAD_NUM; j++) {
      Thread t = new Thread(new Runnable() {
        @Override
        public void run() {
          Thread.currentThread().setName(AtomIntTest.class.getName() + Thread.currentThread().getId());
          for (int i = 0; i < 1000; i++) {
            cas.count(); // i++
            cas.safeCount();
            cas.unsafeCount();
          }
          System.out.println("Thread name: " + Thread.currentThread().getName());
        }
      });
      ts.add(t);
    }
    System.out.println("total thread number: " + ts.size());
    for (Thread t : ts) { // start 600 threads
      t.start();
    }
    // 等待所有线程执行完成
    for (Thread t : ts) {
      try {
        t.join();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
    System.out.println("safe via synchronized: " + cas.i);
    System.out.println("safe: " + cas.atomicI.get());
    System.out.println("unsafe: " + cas.unsafe);
    System.out.println(System.currentTimeMillis() - start);
  }
  /**
   * 
   * 使用CAS实现线程安全计数器
   */
  private void safeCount() {
    for (;;) {
      int i = atomicI.get();
      boolean suc = atomicI.compareAndSet(i, ++i);
      if (suc) {
        break;
      }
    }
  }
  /**
   * 
   * 非线程安全计数器
   */
  synchronized private void count() {
    i++;
  }
  private void unsafeCount() {
    unsafe++;
  }
}