Java并发CopyOnWrite容器原理解析

public boolean add(T e) {
  final ReentrantLock lock = this.lock;
  lock.lock();
  try {
 
    Object[] elements = getArray();
 
    int len = elements.length;
    // 复制出新数组
 
    Object[] newElements = Arrays.copyOf(elements, len + 1);
    // 把新元素添加到新数组里
 
    newElements[len] = e;
    // 把原数组引用指向新数组
 
    setArray(newElements);
 
    return true;
 
  } finally {
 
    lock.unlock();
  }
}
final void setArray(Object[] a) {
  array = a;
}

public E get(int index) {
  return get(getArray(), index);
}

import java.util.Collection;
import java.util.Map;
import java.util.Set;
 
public class CopyOnWriteMap<K, V> implements Map<K, V>, Cloneable {
  private volatile Map<K, V> internalMap;
 
  public CopyOnWriteMap() {
    internalMap = new HashMap<K, V>();
  }
 
  public V put(K key, V value) {
 
    synchronized (this) {
      Map<K, V> newMap = new HashMap<K, V>(internalMap);
      V val = newMap.put(key, value);
      internalMap = newMap;
      return val;
    }
  }
 
  public V get(Object key) {
    return internalMap.get(key);
  }
 
  public void putAll(Map<? extends K, ? extends V> newData) {
    synchronized (this) {
      Map<K, V> newMap = new HashMap<K, V>(internalMap);
      newMap.putAll(newData);
      internalMap = newMap;
    }
  }
}

package com.ifeve.book;
 
import java.util.Map;
 
import com.ifeve.book.forkjoin.CopyOnWriteMap;
 
/**
 * 黑名单服务
 *
 * @author fangtengfei
 *
 */
public class BlackListServiceImpl {
 
  private static CopyOnWriteMap<String, Boolean> blackListMap = new CopyOnWriteMap<String, Boolean>(
      1000);
 
  public static boolean isBlackList(String id) {
    return blackListMap.get(id) == null ? false : true;
  }
 
  public static void addBlackList(String id) {
    blackListMap.put(id, Boolean.TRUE);
  }
 
  /**
   * 批量添加黑名单
   *
   * @param ids
   */
  public static void addBlackList(Map<String,Boolean> ids) {
    blackListMap.putAll(ids);
  }
 
}