Java 写时拷贝容器CopyOnWriteArrayList的测试

package copyOnWriteArrayListTest;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
class AddThread implements Runnable {
    private List<Double> list;
    public AddThread(List<Double> list) {
        this.list = list;
   }
  @Override
   public void run(){
      for ( int i = 0; i < 10000; i++){
        list.add(Math.random());
      }
   }
}
public class CopyOnWriteArrayListTest {
  public static final int THREAD_POOL_SIZE = 2;
  public static void main(String[] args) throws InterruptedException {
    // List<Double> list = new ArrayList<>();
    List<Double> list = new CopyOnWriteArrayList<>();
    ExecutorService es = Executors.newFixedThreadPool(THREAD_POOL_SIZE);
    es.execute(new AddThread(list));
    es.execute(new AddThread(list));
    es.shutdown();
    Thread.sleep(4000);
    System.out.println("OK, list length: " + list.size());
  }
}

/**
     * Appends the specified element to the end of this list.
     *
     * @param e element to be appended to this list
     * @return {@code true} (as specified by {@link Collection#add})
     */
    public boolean add(E e) {
        synchronized (lock) {
            Object[] es = getArray();
            int len = es.length;
            es = Arrays.copyOf(es, len + 1);
            es[len] = e;
            setArray(es);
            return true;
        }
    }